The chaotic opening of Heathrow Terminal 5 contributed to a fifth consecutive year of worsening delays at the world’s busiest international airport.

The Civil Aviation Authority (CAA) said that nearly four in 10 aircraft arriving at Heathrow were delayed during April, May and June.

The figures show a steady worsening in punctuality at the UK’s principle airport as more than three quarters of flights arrived on time five years ago.

Heathrow is operating at maximum capacity so even small problems can escalate into serious delays for both inbound and outbound aircraft.

The chaotic opening of Terminal 5 in March led to long delays for many of the British Airways (BA) flights using the £4.3 billion facility. BA cancelled over 500 flights and misplaced 23,000 bags in the first few weeks the terminal was open.

The CAA does not report how individual flights are delayed but does give average punctuality for each destination. For example, British Airways flights from Heathrow to Vancouver in May were delayed by 73 minutes on average. BA flights to Rome were 37 minutes late - adding one-third to the journey time.

The worst performer for punctuality from Heathrow were Biman flights to Bangladesh, which were nearly 3 hours late on average.

BA said it expects punctuality to improve now that many of the teething problems at T5 have been resolved.

A spokesman for BA said: "Heathrow is the world's most congested two runway airport and operates at maximum capacity every day. Because of the lack of spare runway and air traffic control capacity at Heathrow, there is no slack if minor disruptive incidents occur and little opportunity to avoid knock-on delays for the rest of the day.”

The CAA figures show that in the second quarter of this year 62 per cent of flights were on time, which is classified as being up to 15 minutes late. This was down from 64 per cent in the same period last year and 77 per cent in 2003.

The second quarter figures were an improvement on the winter months when only 56 per cent of planes were on time, although adverse weather conditions often make this quarter bad for delays.

On average planes are 19 minutes late at Heathrow, up from 12 minutes in 2003.

By comparison, 75 per cent of flights from Stansted, Manchester and Edinburgh were on time, 68 per cent from Gatwick and Luton and 77 per cent from Birmingham.

The CAA figures also reveal the worse delayed destinations for passengers leaving the UK from all airports.

The least reliable are to Los Angeles were only half of the 1,611 flights during April, May and June were on time. Passengers travelling to Istanbul, New York, Rome and Chicago also faced long delays to their journey.

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