Almost 1,000 planes a month are late flying into or out of Northern Ireland's two main airports, the Belfast Telegraph can reveal.
New figures obtained by this newspaper show that some 5,180 aircraft failed to arrive or depart within 15 minutes of schedule at Belfast International Airport (BIA) during 2015.
The figure for George Best Belfast City Airport (GBBCA) is higher, at just over 6,450.
The local airports are, however, among the most punctual in the UK - although, according to aviation industry experts, that isn't saying much.
Passengers are more likely to be delayed at British airports than almost anywhere else in the world, largely because runway capacity is being stretched to the limit.
A study by the data company OAG, which took in 196 airports worldwide, showed that the UK's busiest hubs are lagging far behind those in other countries - with seven of them appearing among the worst for delays.
Gatwick was ranked at 192, with more than a third of its flights reported late, Stansted was in 190th place, Luton 189th and Manchester 188th. Glasgow, Edinburgh and Heathrow were all at the bottom of the rankings.
The Northern Ireland airports weren't ranked in the global table because they didn't meet the criteria of handling a minimum of three million departure seats in 2015 - but data was still collected by OAG and it gave a largely favourable impression of BIA and GBBCA.
Belfast International's OTP (on-time performance) rating, for instance, was 83.2% - a figure beaten only by Bristol (88.6%), London City (85.6%) and Birmingham (84.4%)in the UK.
Belfast City, at 83%, was just behind its near neighbour.
City of Derry Airport, incidentally, posted a figure of 72.9%, although this was based on only 65.1% of its traffic and may not be a true reflection of the overall service.
The OAG data shows that BIA handled 2,599,831 airline seats in 2015, with the GBBCA coping with 1,917,278 and Derry 182,385.
The 'late count' for Belfast International was 5,180 out of a total of 30,786 tracked flights; George Best had 6,453 out of 37,901. That adds up to 11,633, an average of 970 late flights per month.
BIA Business Development Director Uel Hoey said he was pleased to note "the general on-time performance" across the airport's network. "Punctuality of service is a critical matter for business and leisure passengers alike, and something which staff across the entire airport business work hard to optimise and maintain," he added.
A spokesman for Belfast City Airport said the majority of flights left on time last year.
"The most common cause of delayed departures at Belfast City Airport is due to late-arriving aircraft," he said.
"In December 2015, 92% of aircraft departing Belfast City Airport did so on time."
According to OAG data, a total of 31,725 flights were recorded at GBBCA last year, with a further 41,032 registered at BIA, and 1,929 at Derry.
Toyko Haneda emerged as the world's most punctual airport, with 91.3% of flights arriving or leaving on time.