Boris Johnson has recruited a fellow mayor from America to boost his campaign to close Heathrow and build a new airport in Kent.
The Mayor of Denver, Colarado, Michael Hancock will speak at a conference in London tomorrow.
Denver moved its international airport in the 1990s despite opposition from major airlines.
City Hall in London claims Denver's experience supports the case for "Boris Island".
Denver International Airport is said to generate $26bn a year and support more than 70,000 jobs.
Boris Johnson said:
"We are world leaders in aviation and people are always going to want to fly to this city.
"But the hub airport we have got is in the wrong place.
"So we should move Heathrow, other cities like Denver have done it and there is no reason why we should not do it too."