The letter to FAA Administrator Stephen Dickson was sent by Rep. Peter DeFazio, D-Ore., chair of the House transportation committee, and Rick Larsen, D-Wash., chair of the Subcommittee on Aviation.
The second concern they cite is a design change to the 787 Dreamliner that removed from the leading edge of the jet's wings a layer of copper foil designed to protect against a lightning strike.
A plane such as the 787 that has a carbon-composite rather than a metal airframe is particularly vulnerable to lightning damage, and a thin layer of copper foil is embedded in areas under the surface of the skin where lightning strikes are common -- especially on the wings, which are full of jet fuel -- to disperse the energy.
In February this year, the FAA office that oversees and certifies Boeing's designs rejected the removal of the foil from the wing edge. Boeing appealed.
DeFazio's letter says that five days later, a company official in a meeting reportedly said that the matter had been discussed with the FAA's Associate Administrator for Aviation Safety, Ali Bahrami. Bahrami has been criticized for his close ties to the aviation manufacturers that the agency oversees.
Two days after that meeting, FAA management reversed course and accepted Boeing's position that the change was acceptable, according to FAA documents.
DeFazio demands to know what the FAA is doing "to ensure that these two issues do not pose a risk to the flying public."
Boeing issued a statement saying it is "aware of both issues raised in Chairman DeFazio's letter."
"We are confident that each was properly considered and addressed by Boeing, thoroughly reviewed with and approved by the FAA," Boeing states.
An FAA spokesman declined to comment, saying that the agency will respond directly to the two legislators.