WASHINGTON (Reuters) - Democratic Senators Richard Blumenthal and Ed Markey called on the Federal Aviation Administration (FAA) to make public all data and information used to justify the Boeing BA.N 737 MAX’s return to service and disclose any internal objections raised by FAA employees. The FAA has proposed requiring a series of software upgrades and other changes to be made before the return of the 737 MAX to service. The airplane has been grounded since March 2019 after two fatal crashes in five months killed 346 people. “Robust transparency is needed to ensure that independent experts and the public can review whether this aircraft is truly safe before it takes to the skies again,” the senators wrote. Boeing declined to comment. The FAA said it would respond directly to the senators. The senators cited reports that suggested the FAA had often yielded to Boeing. “The FAA has demonstrated a disturbing pattern of deferral to Boeing in the past, and we feel strongly that the agency must fully disclose of all information related to its determinations moving forward,” the senators wrote. Separately, major pilots unions said the FAA should require new cockpit procedures for the 737 MAX to help pilots disable an erroneous stall alert that could be a serious distraction during midflight emergencies. The proposal about an erroneous “stick shaker” alert is among recommendations submitted during a 45-day public comment period for the FAA’s proposed 737 MAX design and operating changes. Boeing filed comments proposing changing in wording to various sections of the proposed FAA directive. The 737 MAX changes could pave the way for the FAA to lift a ban on the jet, potentially before year-end. Separately, the Allied Pilots Association, which represents American Airlines" pilots AAL.O, also asked for a checklist to disable erroneous stick shaker activation as well as an overspeed warning.