The series of loud booms heard in Tucson may have been caused by various non-native planes arriving at Davis-Monthan Air Force Base on Tuesday.
A base official said the aircrafts were arriving in preparation for the Heritage Flight Training and Certification Course from Feb. 28 to March 3.
But the official reason for the noise was not known.
"At this moment, we do not have a way of confirming if the sonic boom the community is experiencing was produced by those visiting aircrafts," the official said.
The arriving aircrafts include the F-35 Lighting II, F-22 Raptor and F-16 Fighting Falcon.
During the event, civilian pilots of historic military aircraft and Air Force pilots will practice flying in formation together.
The P-51 Mustang, P-40 Warhawk and F-86 Sabre are some of the historic aircrafts being used in the training.
The certification course event is not an airshow and not open to the public, officials said in a press release. The annual public airshow begins March 23.
Residents can report possible disturbances to Davis-Monthan AFB by using the noise concern form.
So excited to have all of our #HeritageFlight2019 crews out and about at Davis-Monthan AFB! @F22RaptorDemo @A10DemoTeam @ViperDemoTeam @F35Demo and the @afhflight foundation! https://t.co/hZIXFztMPW
— Davis-Monthan AFB (@DMAFB) February 26, 2019