The number of complaints made by air travellers almost trebled last year, according to an official passenger watchdog.
The Air Transport Users Council (AUC) said 6,000 written complaints were received in 2005/06.
Nearly two-thirds of the written grievances concerned cancellations and delays, while recorded complaints about mislaid baggage also increased.
The number of telephone complaints received by the AUC also increased from 3,514 in 2004/05 to 3,755 in 2005/06.
Over the year, 1,983 written complaints were received by the watchdog about cancellations, a dramatic increase on the 297 made during the previous 12 months.
The number of telephone protests made about cancellations increased from 427 to 583.
Written complaints about delays also rose from 436 to 1,969 in 2005/06, while corresponding telephone complaints rose from 446 to 711.
Meanwhile, some 458 people made written complaints about mishandled baggage in 2005/06, compared to 323 in the previous year.
The AUC had anticipated a large increase in passenger complaints following the introduction of new EU rules giving air travellers rights to compensation in response to delayed, cancelled or overbooked flights.
But the watchdog warned that while airlines had generally worked to ensure that passengers received their new entitlements, many companies needed to improve their performance.
"We know from discussions with airlines that, for the most part, they have worked hard to ensure that passengers receive their entitlements under the new EC regulation," said the chairman of the AUC, Tina Tietjen.
"However, the main message coming out of our complaints work appears to be that company policy is still not consistently applied at ground level," she added.
"There remain too many occasions when those suffering delays and cancellations are often not getting their full entitlements."