From 4 April this year, the volume allowed for the single bag allowed to qualify for Spirit’s “Bare Fare” shrinks from 2,688 to 2,016 cubic inches.

Passengers whose oversized cabin bag is identified at the boarding gate will typically pay a penalty of $100 to take it on board. Travellers can pay in advance for larger pieces of cabin baggage, starting at $26.

Spirit is based near Miami in Florida, and has an extensive network across the US as well as the Caribbean and Latin America.

The move comes after two “full-service” rivals, American Airlines and United, introduced Basic Economy fares. The cheap tickets are aimed at countering the rapid growth of “ultra-low-cost” carriers such as Spirit and Frontier.

The travel blogger Ben Schlappig, who runs the One Mile At A Time site, said: "You know it’s a sad day when Spirit Airlines makes their policy worse so they’re not being more generous than the legacy carriers."

The two leading European budget airlines are much more generous in their cabin-baggage policies: easyJet’s allowance is almost twice as big, while Ryanair offers one-third more volume as well as the chance to take a second bag on board free of charge.