SturdiBag Pro (Large, Flexible Height) — dimensions & which airlines it fits
SturdiBag Pro (Large, Flexible Height): 18 × 11.5 × 11.5 in external. The flexible-height top is the whole point — it compresses down to slide under lower seats, then springs back. A common pick for the 8.5" airlines (compresses; verify for your specific seat).
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Specs
| External size (L×W×H) | 18 × 11.5 × 11.5 in |
| Type | soft-sided · flexible height |
Dimensions from the manufacturer product page · verified 2026-09-04
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Which airlines does the SturdiBag Pro (Large, Flexible Height) fit?
Compared against each airline's published under-seat limit (height strict; footprint may rotate). Green = within the published size; amber = fits only when collapsed / flexed; grey = over.
| Airline | Its limit | This carrier |
|---|---|---|
| Pegasus Airlines | 19.7 × 12.6 × 12.6 in | Fits 18 × 11.5 × 11.5 in is within 19.7 × 12.6 × 12.6 in — 1.7" spare on length, 1.1" on width, 1.1" on height. |
| Saudia | 21 × 16 × 13 in | Fits 18 × 11.5 × 11.5 in is within 21 × 16 × 13 in — 3" spare on length, 4.5" on width, 1.5" on height. |
| airBaltic | 21.7 × 15.7 × 9.1 in | Flexes — 2.4" over 11.5" tall vs a 9.1" limit — 2.4" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. |
| Allegiant Air | 18 × 12 × 11 in | Flexes — 0.5" over 11.5" tall vs a 11" limit — 0.5" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. |
| Austrian Airlines | 21.7 × 15.7 × 9.1 in | Flexes — 2.4" over 11.5" tall vs a 9.1" limit — 2.4" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. |
| Avianca | 22 × 14 × 10 in | Flexes — 1.5" over 11.5" tall vs a 10" limit — 1.5" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. |
| Brussels Airlines | 21.7 × 15.7 × 9.1 in | Flexes — 2.4" over 11.5" tall vs a 9.1" limit — 2.4" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. |
| Condor | 21.6 × 15.7 × 9 in | Flexes — 2.5" over 11.5" tall vs a 9" limit — 2.5" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. |
| Contour Airlines | 24 × 16 × 10 in | Flexes — 1.5" over 11.5" tall vs a 10" limit — 1.5" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. |
| Discover Airlines | 21.7 × 15.7 × 9.1 in | Flexes — 2.4" over 11.5" tall vs a 9.1" limit — 2.4" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. |
| Edelweiss | 21.7 × 15.7 × 9.1 in | Flexes — 2.4" over 11.5" tall vs a 9.1" limit — 2.4" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. |
| Eurowings | 21.7 × 15.7 × 9.1 in | Flexes — 2.4" over 11.5" tall vs a 9.1" limit — 2.4" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. |
| Finnair | 21.7 × 15.7 × 7.9 in | Flexes — 3.6" over 11.5" tall vs a 7.9" limit — 3.6" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. |
| Frontier Airlines | 18 × 14 × 11 in | Flexes — 0.5" over 11.5" tall vs a 11" limit — 0.5" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. · full fit check → |
| ITA Airways | 21.7 × 15.7 × 9.1 in | Flexes — 2.4" over 11.5" tall vs a 9.1" limit — 2.4" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. |
| Lufthansa | 21.7 × 15.7 × 9.1 in | Flexes — 2.4" over 11.5" tall vs a 9.1" limit — 2.4" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. |
| Porter Airlines | 21.5 × 15.5 × 10.5 in | Flexes — 1" over 11.5" tall vs a 10.5" limit — 1" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. |
| Royal Air Maroc | 21.7 × 15.7 × 7.9 in | Flexes — 3.6" over 11.5" tall vs a 7.9" limit — 3.6" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. |
| Swiss International Air Lines | 21.7 × 15.7 × 9.1 in | Flexes — 2.4" over 11.5" tall vs a 9.1" limit — 2.4" over, but the flexible-height top compresses down. Verify it squeezes under your actual seat. |
| Aegean Airlines | 15.7 × 9.8 × 9.8 in | Too big 18 × 11.5 × 11.5 in is over the 15.7 × 9.8 × 9.8 in limit. |
| Air Canada | 17 × 16 × 8 in | Too big 18 × 11.5 × 11.5 in is over the 17 × 16 × 8 in limit. · full fit check → |
| Air Europa | 15.7 × 11.8 × 11.8 in | Too big 18 × 11.5 × 11.5 in is over the 15.7 × 11.8 × 11.8 in limit. |
| Air France | 18.1 × 11 × 9.4 in | Too big 18 × 11.5 × 11.5 in is over the 18.1 × 11 × 9.4 in limit. |
| Air Transat | 17 × 9.5 × 10 in | Too big 18 × 11.5 × 11.5 in is over the 17 × 9.5 × 10 in limit. |
| Alaska Airlines | 17 × 11 × 9.5 in | Too big 18 × 11.5 × 11.5 in is over the 17 × 11 × 9.5 in limit. · full fit check → |
| Alaska Horizon (Horizon Air) | 17 × 11 × 9.5 in | Too big 18 × 11.5 × 11.5 in is over the 17 × 11 × 9.5 in limit. |
| American Airlines | 18 × 11 × 11 in | Too big 18 × 11.5 × 11.5 in is over the 18 × 11 × 11 in limit. · full fit check → |
| American Eagle (regional, incl. Republic Airways) | 18 × 11 × 11 in | Too big 18 × 11.5 × 11.5 in is over the 18 × 11 × 11 in limit. |
| Asiana Airlines | 17.7 × 12.6 × 8.2 in | Too big 18 × 11.5 × 11.5 in is over the 17.7 × 12.6 × 8.2 in limit. |
| Avelo Airlines | 17 × 9 × 13 in | Too big 18 × 11.5 × 11.5 in is over the 17 × 9 × 13 in limit. |
| Azul Linhas Aéreas | 16.9 × 12.4 × 7.8 in | Too big 18 × 11.5 × 11.5 in is over the 16.9 × 12.4 × 7.8 in limit. |
| Breeze Airways | 17 × 8 × 13 in | Too big 18 × 11.5 × 11.5 in is over the 17 × 8 × 13 in limit. |
| Cape Air | 17 × 12.5 × 8.5 in | Too big 18 × 11.5 × 11.5 in is over the 17 × 12.5 × 8.5 in limit. |
| Copa Airlines | 18 × 11 × 11 in | Too big 18 × 11.5 × 11.5 in is over the 18 × 11 × 11 in limit. |
| Delta Air Lines | 18 × 11 × 11 in | Too big 18 × 11.5 × 11.5 in is over the 18 × 11 × 11 in limit. · full fit check → |
| EL AL Israel Airlines | 13 × 8 × 7 in | Too big 18 × 11.5 × 11.5 in is over the 13 × 8 × 7 in limit. |
| Etihad Airways | 15.7 × 15.7 × 8.7 in | Too big 18 × 11.5 × 11.5 in is over the 15.7 × 15.7 × 8.7 in limit. |
| GOL Linhas Aéreas | 16.9 × 12.6 × 9.4 in | Too big 18 × 11.5 × 11.5 in is over the 16.9 × 12.6 × 9.4 in limit. |
| Hawaiian Airlines | 17 × 11 × 9.5 in | Too big 18 × 11.5 × 11.5 in is over the 17 × 11 × 9.5 in limit. |
| Iberia | 17.7 × 13.8 × 9.8 in | Too big 18 × 11.5 × 11.5 in is over the 17.7 × 13.8 × 9.8 in limit. |
| JetBlue | 17 × 12.5 × 8.5 in | Too big 18 × 11.5 × 11.5 in is over the 17 × 12.5 × 8.5 in limit. |
| JSX | 17 × 13 × 11 in | Too big 18 × 11.5 × 11.5 in is over the 17 × 13 × 11 in limit. |
| KLM Royal Dutch Airlines | 18.1 × 11 × 9.4 in | Too big 18 × 11.5 × 11.5 in is over the 18.1 × 11 × 9.4 in limit. |
| Korean Air | 17.5 × 12.5 × 7.5 in | Too big 18 × 11.5 × 11.5 in is over the 17.5 × 12.5 × 7.5 in limit. |
| LATAM Airlines | 15.7 × 11 × 9.8 in | Too big 18 × 11.5 × 11.5 in is over the 15.7 × 11 × 9.8 in limit. |
| LOT Polish Airlines | 17.7 × 11.8 × 7.9 in | Too big 18 × 11.5 × 11.5 in is over the 17.7 × 11.8 × 7.9 in limit. |
| Norwegian | 16.9 × 12.2 × 7.9 in | Too big 18 × 11.5 × 11.5 in is over the 16.9 × 12.2 × 7.9 in limit. |
| SAS Scandinavian Airlines | 15.7 × 9.8 × 9.1 in | Too big 18 × 11.5 × 11.5 in is over the 15.7 × 9.8 × 9.1 in limit. |
| Southwest Airlines | 18 × 10.5 × 10 in | Too big 18 × 11.5 × 11.5 in is over the 18 × 10.5 × 10 in limit. · full fit check → |
| Sun Country Airlines | 17 × 12 × 9 in | Too big 18 × 11.5 × 11.5 in is over the 17 × 12 × 9 in limit. |
| TAP Air Portugal | 17.7 × 11.8 × 9 in | Too big 18 × 11.5 × 11.5 in is over the 17.7 × 11.8 × 9 in limit. |
| Transavia | 15.7 × 11.8 × 9.4 in | Too big 18 × 11.5 × 11.5 in is over the 15.7 × 11.8 × 9.4 in limit. |
| Turkish Airlines | 15.7 × 11.8 × 9.1 in | Too big 18 × 11.5 × 11.5 in is over the 15.7 × 11.8 × 9.1 in limit. |
| United Airlines | 18 × 11 × 11 in | Too big 18 × 11.5 × 11.5 in is over the 18 × 11 × 11 in limit. · full fit check → |
| Viva Aerobus | 17.3 × 13.8 × 8.3 in | Too big 18 × 11.5 × 11.5 in is over the 17.3 × 13.8 × 8.3 in limit. |
| Volaris | 17.3 × 11.8 × 7.5 in | Too big 18 × 11.5 × 11.5 in is over the 17.3 × 11.8 × 7.5 in limit. |
| Vueling | 17.7 × 15.4 × 8.3 in | Too big 18 × 11.5 × 11.5 in is over the 17.7 × 15.4 × 8.3 in limit. |
| WestJet | 16 × 10 × 8.5 in | Too big 18 × 11.5 × 11.5 in is over the 16 × 10 × 8.5 in limit. |
| Aeroméxico | not published | Size not published Aeroméxico does not publish a maximum carrier size, so we will not compute a fit. Confirm the under-seat allowance with Aeroméxico before you book. |
| Croatia Airlines | not published | Size not published Croatia Airlines does not publish a maximum carrier size, so we will not compute a fit. Confirm the under-seat allowance with Croatia Airlines before you book. |
| Mokulele Airlines | not published | Size not published Mokulele Airlines does not publish a maximum carrier size, so we will not compute a fit. Confirm the under-seat allowance with Mokulele Airlines before you book. |
| Southern Airways Express | not published | Size not published Southern Airways Express does not publish a maximum carrier size, so we will not compute a fit. Confirm the under-seat allowance with Southern Airways Express before you book. |
| Aer Lingus | not published | No cabin pets Aer Lingus does not accept pets in the cabin, so carrier size is not the deciding factor. Check Aer Lingus's own policy for cargo or approved pet-shipper options. |
| Air New Zealand | not published | No cabin pets Air New Zealand does not accept pets in the cabin, so carrier size is not the deciding factor. Check Air New Zealand's own policy for cargo or approved pet-shipper options. |
| ANA (All Nippon Airways) | not published | No cabin pets ANA (All Nippon Airways) does not accept pets in the cabin, so carrier size is not the deciding factor. Check ANA (All Nippon Airways)'s own policy for cargo or approved pet-shipper options. |
| British Airways | not published | No cabin pets British Airways does not accept pets in the cabin, so carrier size is not the deciding factor. Check British Airways's own policy for cargo or approved pet-shipper options. |
| Cathay Pacific | not published | No cabin pets Cathay Pacific does not accept pets in the cabin, so carrier size is not the deciding factor. Check Cathay Pacific's own policy for cargo or approved pet-shipper options. |
| China Airlines | not published | No cabin pets China Airlines does not accept pets in the cabin, so carrier size is not the deciding factor. Check China Airlines's own policy for cargo or approved pet-shipper options. |
| easyJet | not published | No cabin pets easyJet does not accept pets in the cabin, so carrier size is not the deciding factor. Check easyJet's own policy for cargo or approved pet-shipper options. |
| Emirates | not published | No cabin pets Emirates does not accept pets in the cabin, so carrier size is not the deciding factor. Check Emirates's own policy for cargo or approved pet-shipper options. |
| Icelandair | not published | No cabin pets Icelandair does not accept pets in the cabin, so carrier size is not the deciding factor. Check Icelandair's own policy for cargo or approved pet-shipper options. |
| Japan Airlines | not published | No cabin pets Japan Airlines does not accept pets in the cabin, so carrier size is not the deciding factor. Check Japan Airlines's own policy for cargo or approved pet-shipper options. |
| Qantas | not published | No cabin pets Qantas does not accept pets in the cabin, so carrier size is not the deciding factor. Check Qantas's own policy for cargo or approved pet-shipper options. |
| Qatar Airways | not published | No cabin pets Qatar Airways does not accept pets in the cabin, so carrier size is not the deciding factor. Check Qatar Airways's own policy for cargo or approved pet-shipper options. |
| Ryanair | not published | No cabin pets Ryanair does not accept pets in the cabin, so carrier size is not the deciding factor. Check Ryanair's own policy for cargo or approved pet-shipper options. |
| Singapore Airlines | not published | No cabin pets Singapore Airlines does not accept pets in the cabin, so carrier size is not the deciding factor. Check Singapore Airlines's own policy for cargo or approved pet-shipper options. |
| Virgin Atlantic | not published | No cabin pets Virgin Atlantic does not accept pets in the cabin, so carrier size is not the deciding factor. Check Virgin Atlantic's own policy for cargo or approved pet-shipper options. |
"Fits" here means it's within the published maximum — the actual space under your seat varies by aircraft. See why →
Compared with
SturdiBag Pro (Large, Flexible Height) vs Sherpa Original Deluxe (Large) SturdiBag Pro (Large, Flexible Height) vs Sleepypod Air SturdiBag Pro (Large, Flexible Height) vs Diggs Passenger SturdiBag Pro (Large, Flexible Height) vs Away The Pet Carrier
Not sure this is the one? See the best carriers ranked by how many airlines they fit · compare all: carriers · fit for a specific airline: Aegean Airlines · Aer Lingus · Aeroméxico · Air Canada · Air Europa
Common questions
What are the dimensions of the SturdiBag Pro (Large, Flexible Height)?
Its published external size is 18 × 11.5 × 11.5 in. Source: the manufacturer's product page.
Which airlines does the SturdiBag Pro (Large, Flexible Height) fit?
Against published limits it fits Pegasus Airlines, Saudia, airBaltic, Allegiant Air, Austrian Airlines, Avianca, Brussels Airlines, Condor, Contour Airlines, Discover Airlines, Edelweiss, Eurowings, Finnair, Frontier Airlines, ITA Airways, Lufthansa, Porter Airlines, Royal Air Maroc, Swiss International Air Lines, Aeroméxico, Croatia Airlines, Mokulele Airlines, Southern Airways Express, Aer Lingus, Air New Zealand, ANA (All Nippon Airways), British Airways, Cathay Pacific, China Airlines, easyJet, Emirates, Icelandair, Japan Airlines, Qantas, Qatar Airways, Ryanair, Singapore Airlines, Virgin Atlantic. Real under-seat space varies by aircraft, so confirm for your flight.