The aviation industry had hoped that last week's relaxation of cabin baggage rules, allowing passengers to take more on board with the consent of the airline, would simplify a confusing situation. Instead, the latest change appears to have made matters worse - with Britain's leading airport operator, BAA, giving passengers conflicting information depending on which airport they are using.

Starting on 22 September, the Department for Transport decreed that the maximum size for the single piece of baggage allowed through the central search areas at Britain's airports would increase to the internationally agreed standard: length of 56cm, a width of 45cm and a depth of 25cm. This works out at a volume of 63 litres, compared with the previous limit of 25 litres, and is enough for most modest-sized roller-cases.

BAA is repeating this message for passengers at Heathrow and Gatwick. But passengers using Stansted are being given leaflets that insist the maximum size allowed is substantially smaller: 55cm x 40cm x 20cm, representing a volume of 44 litres. However, easyJet, which has a large operation at Stansted, allows passengers to take substantially bigger bags: up to the Department for Transport size limit and with no weight restriction. Toby Nicol of easyJet said "It's one thing for an airline to stipulate a lower size of hand luggage, but we find it unacceptable that an airport should do the same."

A spokesman for BAA said "It's purely practical because the biggest airline at Stansted is Ryanair. We're trying to get a complex message through as simply as possible." Ryanair imposes the lower limit, in addition to a strict weight limit of 10kg.

Both easyJet and Ryanair also use Gatwick airport, where passengers are told that the larger limits apply. Many travellers are now checking in online, which means that the first encounter they have with airline staff is at the departure gate.

Ryanair is incentivising passengers who check in online by allowing them priority boarding, even ahead of families with young children. But the Irish airline warns that passengers who use online check-in but exceed its cabin baggage specifications will be obliged to check in the offending item and pay a "boarding card re-issue fee", currently £13.50. The chief executive of easyJet, Andy Harrison, has called for the rules to be relaxed still further: "We hope our passengers will soon be allowed to take a second bag, such as a laptop, into the cabin."

FlyBE, which has a dense network of UK regional and international flights, has smaller limits than Ryanair, because it uses smaller aircraft: 50cm x 35cm x 23cm, giving a total volume of 40 litres.

Other airlines, particularly charters, impose strict limits on weight: 5kg is typical. This is supposed to include any shopping done at the airport.

British Airways' frequent flyers, who have experienced six different baggage regimes in the past two months, may be even more baffled about the amount that can be carried on board. On the eve of the relaxation of rules on size, 300,000 members of BA's Executive Club were sent an e-mail that appeared to contradict government announcements by maintaining that the old, small- er dimensions would continue in force. The airline blamed a "technical error", and has confirmed that the higher limits now apply.