PASSENGERS suffered delays on more than one in four flights at Scottish airports last year - with Edinburgh performing the worst.
Punctuality at both Edinburgh and Glasgow has also fallen in each of the last three years, according to new statistics.
The slump in time-keeping has accompanied major aviation growth, but the airports said most hold-ups were caused by airlines or factors such as bad weather, strikes and the need to reform congested airspace.
Flights at Edinburgh suffered the most delays in the year to March, according to analysis of official Civil Aviation Authority (CAA) figures by consumer group Which?
A total of 27.3 per cent of its 112,000 flights were more than 15 minutes late - the industry measure - compared to 15 per cent in 2013-14. Average delays increased from nine to nearly 15 minutes.
The airport handled an extra million passengers each year over that period, which have now reached 12.7 million annually.
At Glasgow, 25 per cent of nearly 85,000 flights were late, compared to almost 16 per cent three years ago. The airport has grown from 8 to 9.5 million passengers.
The CAA, the UK’s aviation regulator, said the industry must do better. Its spokesman said: “Getting to your destination on time is incredibly important to passengers, and any delay causes understandable frustration.
“While it is clear airports in Scotland are getting busier, with more flights arriving and departing and more people passing through terminals, this should not be at the expense of punctuality.
“To ensure on-time performance improves, we expect airlines, airports and air traffic control to work together and address any issues.”
Edinburgh Airport said the problem largely lay elsewhere, and there had been a “great improvement” this year, with far fewer delays.
Its spokesman said: “On-time performance is important to our passengers and is a measure we monitor very closely. Frustratingly, it is mainly affected by factors outwith the airport’s control.
“We continue to work with our airline and aviation partners to make sure our collective performance is as good as it can be and that we are in the best position to deal with the external issues that affect us.”
However, Ryanair, which is the second biggest at Edinburgh, said major work where aircraft are boarded had caused delays for all airlines.
A spokesman for National Air Traffic Services said: “Delays occur for a very wide range of reasons, the vast majority of which will be totally non-air traffic control related. ”However, the proportion of flights delayed by more than three hours, when passengers can claim compensation, has not significantly changed.
They amounted to 0.5 per cent of flights at Edinburgh and Glasgow last year - 560 and 420 respectively. This was 0.1 points higher in Edinburgh than three years ago and 0.1 points lower in Glasgow.