The prime minister has been urged by 50 politicians to give the green light to a new runway at Heathrow.
The group from Wales, Scotland and Northern Ireland called on Theresa May to approve a third runway at the airport, describing it as “our gateway to the world”.
The government could make a decision as early as this week.
Mrs May is believed not to favour a compromise option that would see both Heathrow and Gatwick build new runways.
The group urging the prime minister to approve Heathrow expansion includes Welsh Conservative MP and former cabinet minister Stephen Crabb, Northern Irish DUP deputy leader Nigel Dodds and Welsh Labour’s Stephen Kinnock.
All three signed the letter to Mrs May which argued: “Although Heathrow is in London, it is the UK’s hub airport.
“Other countries are investing in and supporting their hub, or looking on enviously as they hub through other countries.
“Northern Ireland, Scotland and Wales all have our own successful and growing airports.
“But Heathrow is our gateway to the world, bringing tourists to our attractions and helping our exporters reach new markets.
“Whether we are connected by road, rail or air, we know that connections to Heathrow are a key driver of investment decisions.
“Expanding Heathrow will create nearly four times more jobs in our three nations than other options being considered.”
‘Fight tooth and nail’
Mrs May faces considerable opposition to a third runway at Heathrow within her own cabinet as well as the Conservative Party and former Prime Minister David Cameron repeatedly put off making a decision.
Tory MP Adam Afriyie said he would vote against Heathrow expansion in defiance of party whips if there was no free vote in the House of Commons.
The Windsor MP told the BBC’s Sunday Politics show: “Oh, 100% yes. I’m going to fight tooth and nail.”
Conservative MP MP Zac Goldsmith has already warned Mrs May she faces losing Conservative MPs and councils if she backs Heathrow expansion.
The former London mayoral candidate has promised to quit as an MP if Mrs May give her backing to a third runway at the airport.
Fellow Tory MP Kwasi Kwarteng said reports that there are 60 opponents within the party are “way off the mark”, telling the programme there are about “20 hardcore people” .
A cabinet sub-committee is due to meet, possibly as early as this week, to examine the arguments for the three options set out in last year’s Airports Commission report.
The commission recommended in July 2015 that a third runway should be built at Heathrow.
Other options are extending the airport’s existing northern runway or building a second runway at Gatwick
Politicians urge May to back Heathrow third runway}