The lawmakers said that if the FCC walks away from LightSquared it would "ignore a decade of regulatory rules and orders on which this business relied in building their model."
They said the FCC should either move LightSquared to new airwaves or develop a technical solution that would eliminate the interference problem.
"I hope that the FCC will examine all possibilities to allow this broadband competitor to move forward, while ensuring a more robust GPS system for the American consumer," the lawmakers wrote.
Government testing showed that while LightSquared's signal does not bleed into the GPS band, GPS receivers are too sensitive to filter out LightSquared's powerful cell towers operating on nearby frequencies.
LightSquared argues it is the GPS industry's responsibility to build receivers that only listen to their own designated frequencies, but GPS companies claim LightSquared is trying to build a cellphone network relying on frequencies that should only be used by satellites, which transmit much fainter signals.
Some Republicans have questioned whether the administration showed inappropriate favoritism to LightSquared. Sen. Chuck Grassley (R-Iowa) has blocked President Obama's two nominees to the FCC in an effort to force the agency to release internal records on its review of the company.
Republicans on the House Energy and Commerce Committee have launched their own probe into the FCC's handling of LightSquared. They question why the agency allowed LightSquared to get as far as it did in the regulatory process.
The White House and the FCC have denied giving any special treatment to LightSquared, but expanding high-speed Internet access is a priority for the administration.