(Adds more details, background, Boeing declining to comment)
By David Shepardson
WASHINGTON, Nov 29 (Reuters) - U.S. lawmakers are holding intensive discussions about whether to extend a key certification deadline for two new versions of Boeing's best-selling 737 MAX, lawmakers and aides said.
The largest U.S. planemaker is seeking an extension from Congress of a December deadline imposing a new safety standard for modern cockpit alerts for the 737 MAX 7 and 737 MAX 10 variants.
"We do want to push for safety enhancements and we'll see what happens - some people just want a straight extension," Senate Commerce Committee Chair Maria Cantwell told Reuters late on Tuesday, saying there is no agreement yet.
The requirements were adopted by Congress as part of certification reform passed after two fatal 737 MAX crashes killed 346 people in Indonesia and Ethiopia and led to the plane's 20-month grounding.
Boeing declined to comment Tuesday, but Chief Executive Dave Calhoun said in October he was confident it will get the extension.
After Dec. 27, all planes must have modern cockpit alerting systems to be certified by the Federal Aviation Administration (FAA), which would mean significant delays for the new MAX aircrafts' deployment unless Congress grants a waiver to extend the deadline. In September, Senator Roger Wicker, the top Republican on the Commerce Committee, proposed extending the deadline for Boeing to win approval for the two new variants until September 2024.
"It should be extended," Wicker told Reuters on Monday, referring to the deadline. "I think it needs to happen."
Committee Chair Cantwell said Tuesday, "We're trying to get some information from the FAA and we're going to talk to our counterparts here." She declined to say what conditions she might seek to attach.
"Safety should be the focus, not a date, safety," Cantwell said.
Boeing has won significant support for an extension from lawmakers, the U.S. Chamber of Commerce but faces strong opposition from relatives of many victims of the two fatal crashes, arguing Boeing was "bullying" Congress into action.
Earlier this month, acting FAA Administrator Billy Nolen said he does not expect the agency will certify the 737 MAX 7 before the December deadline.
Nolen said he believes the FAA cannot continue any MAX certification work after the deadline without action from Congress.
Boeing said in October it expected the 737 MAX 7 to be certified this year or in 2023 and the MAX 10 to begin FAA certification flight testing in 2022 or 2023 and enter service in 2023 or 2024. (Reporting by David Shepardson; Editing by Chris Reese and Kenneth Maxwell)