U.S. pilots expressed confidence in their ability to safely fly their airlines' Boeing 737 Max planes and said it is too early to know what brought down one of the planes in Ethiopia over the weekend, the second fatal crash of one of the bestselling aircraft in less than five months.

The Allied Pilots Association, which represents about 15,000 American Airlines pilots, broke from flight attendants and mechanics in backing the plane. The pilots' group said they "have the necessary training and experience to troubleshoot problems and take decisive actions on the flight deck to protect our passengers and crew."

United's pilots union, the Air Line Pilots Association, issued a similar statement.

The statements come after airlines and governments around the world said they grounded the planes as a precaution. The Federal Aviation Administration has repeatedly said it does not see any reason to order the planes be taken out of service. Still, lawmakers, travelers and flight attendants and other airline employees called for the planes to be grounded until more is known about the cause of the Ethiopian Airlines crash.

On Wednesday, Sen. Roger Wicker, R-Miss., the chairman of the Committee on Commerce, Science and Transportation, said the committee is planning an aviation safety hearing in light of the crash.

The FAA on Tuesday reiterated its position that it does not have any reason to ground the planes.

American Airlines has 24 Boeing 737 Max 8 planes in its fleet of about 1,000 mainline aircraft. Following the crash of Lion Air Flight 610 in October, which plunged into the Java Sea after taking off from Jakarta, Indonesia, killing all 189 people on board, American's pilots union said it has reviewed flight data of more than 14,000 flights.

The pilots of the Lion Air plane, another Boeing 737 Max 8, appeared to be battling an automated system that pushes the nose of the plane downward to prevent stalling, investigators have indicated. That can be catastrophic if the plane is receiving erroneous data that signal the plane is in a stall. Boeing on Monday said it is preparing a series of software fixes as well as updates to training and manuals for the planes, its bestselling aircraft. It said those changes are "designed to make an already safe aircraft even safer."

"We have not seen a single anomaly" related to the maneuvering characteristics augmentation system, known as the MCAS, American's pilot union APA said in a statement.

American added optional cockpit displays for its Boeing 737s that show if there is a disagreement between sensors showing the so-called angle of attack, which is the angle of the plane relative to the oncoming air, and the actual angle.

Southwest Airlines, the biggest U.S. operator of Boeing 737 Max planes with 34 in its fleet of more than 750 planes, told CNBC it added such displays after the crash of Lion Air in October.

For its part, United's union said that its review of more than 23,000 hours of flying show that none of "these data points has been attributable to performance or mechanical deficiencies."