The shelf
Choose a carrier and a slot and the shelf narrows to what clears it. Sides are compared largest to largest, which is the comparison the airport sizer makes.
5 / 18 frames
40 × 30 × 20 cm · under-seat · 5.0 / 5
$59.55seen November 2026
5 / 18 frames
40 × 30 × 20 cm · under-seat · 4.7 / 5
$79.13seen November 2026
5 / 18 frames
40 × 30 × 20 cm · under-seat · 4.7 / 5
$80.60seen November 2026
5 / 18 frames
40 × 30 × 20 cm · under-seat · 4.6 / 5
$53.47seen November 2026
5 / 18 frames
40 × 30 × 20 cm · under-seat · 4.6 / 5
$63.10seen November 2026
6 / 18 frames
40 × 25 × 20 cm · under-seat · 4.7 / 5
$70.58seen November 2026
6 / 18 frames
40 × 25 × 20 cm · under-seat · 4.6 / 5
$68.10seen November 2026
0 / 18 frames
45 × 36 × 20 cm · under-seat · 4.7 / 5
$100.34seen November 2026
0 / 18 frames
45 × 36 × 20 cm · under-seat · 4.7 / 5
$61.95seen November 2026
15 / 18 frames
46 × 36 × 20 cm · locker · 5.0 / 5
$117.79seen November 2026
9 / 18 frames
56 × 36 × 23 cm · locker · 4.7 / 5
$62.33seen November 2026
4 / 18 frames
55 × 40 × 20 cm · locker · 4.6 / 5
$70.08seen November 2026
No bag here meets that frame. Switch the slot and look again — an underseat bag will usually take a locker, but the reverse almost never works.
The arithmetic
Take a 46 × 36 × 20 bag and a 40 × 30 × 20 frame: it fails on two sides whichever way you turn it. Against a 55 × 38 × 20 locker the same bag passes. Sorting each triplet first is what lets a bag be laid any way up.