Fewer flights leaving from and arriving at Heathrow Airport were delayed this year, recent figures suggest.

An aviation workers' union said flight delays are a lasting consequence of the Covid-19 pandemic, and warned of lingering staff shortages across the country.

The Civil Aviation Authority – the UK's aviation regulator – and the Department for Transport are working to create a UK Airspace Design Service, aimed at reducing flight delays, emissions and noise pollution.

Recent CAA figures suggest 21% of flights leaving from and arriving at Heathrow Airport were delayed by at least 15 minutes in March.

It was down from 26% a year earlier, and above the 18% average across 25 of the UK's largest commercial airports.

A total of 39,914 flights left from and arrived at Heathrow Airport in March, and they were delayed by an average of 11 minutes.

The average flight delay across UK airports was nine minutes in March – down from 12 a year earlier.

And the proportion of flights delayed varied significantly; 24% of flights to and from Newcastle Airport were delayed by at least 15 minutes in March, compared to 8% for Leeds Bradford Airport.

The Union of Pilots, Engineers and Cabin Crew welcomed the declining proportion of flight delays across UK airports.

A spokesperson said the Covid-19 pandemic "materially damaged" the aviation sector, and enduring delays are part of a "long and painful process" to recover from the crisis.

They said: "Airlines across the UK have attacked the issues of delays with the utmost diligence."

But they warned there is a "critical shortage" of pilots and engineers which may affect the recovery from delays, as well as flight cancellation levels.

The figures show 1.8% of flights to and from UK airports were cancelled in March – up from 1% the previous year.

Anna Bowles, head of consumers at the CCA, said: "The majority of airlines have made progress in reducing delays, with the average falling.

"Delays occur for many reasons, and can cause significant disruption and inconvenience to passengers.

"We fully expect that airlines minimise the impact by providing timely information and upholding passengers' rights during disruption."