Burnham dodges questions on Heathrow third runway as project faces four-year delay

Airport chiefs say 2035 operations deadline unachievable as critics say new delay makes case for project ‘even more dubious’

Plans for a third runway at Heathrow are once again up in the air after the prime minister refused to say whether he backs the “contested” project which is delayed by up to four years.

Over the weekend it emerged that ​Heathrow no longer expects to meet the original 2035 deadline. Instead, the airport hopes to secure planning permission by 2029 and then open the runway “within a decade”, meaning it would not be operational until 2039.