New correspondence between an unconventional group of allies is shedding light on the high-stakes fight to prevent more flights at lawmakers’ favorite airport.

Over the course of the last year, United Airlines lobbyists worked with Washington, D.C.’s local airport authority as well as staff to Virginia lawmakers to coordinate strategy and messaging in a bid to keep Congress from approving additional flights at Ronald Reagan Washington National Airport, one of the busiest travel hubs in the country.