"Aviation use of GPS would be significantly compromised," said Peter Appel, administrator of the department's Research and Innovation Technology Administration.

Most of the witnesses and some lawmakers on the committee called for additional testing of LightSquared's proposal to use only the lower band of spectrum for now, which it submitted on June 30. LightSquared Executive Vice President Jeffrey Carlisle said about 130 products were tested in that band during a series of tests earlier this year.

However, LightSquared has now submitted to the FCC to try to find a solution to the interference, Carlisle said. In the paper filed Wednesday, the company proposed committing itself to a certain level of broadcast power from its LTE towers, measured on the ground at various distances from each tower.

The company also proposed providing a stable satellite signal for GPS augmentation services, which high-precision GPS units use, at a different part of LightSquared's band.

"This is not a zero-sum game," Carlisle said, expressing confidence that a solution can be found to allow both GPS and LightSquared's network to operate. He estimated that only 500,000 to 750,000 high-precision GPS devices would be affected by an LTE network running in LightSquared's lower band. Nevertheless, he told lawmakers that his company planned to spend $14 billion over the next eight years to build and run the network and that interference was caused by problems with receivers that GPS vendors should have known about but never addressed.