A loud explosion may have woken up some Central Floridians Sunday morning, but those who have lived here a while recognized the sounds of a sonic boom.

  • X-37B mini-shuttle returned to Kennedy Space Center Sunday
  • Landing caused a sonic boom
  • Mini-shuttle has spent over 700 days in space
  • RELATED: Rocket launch schedule

A top secret Air Force mini-shuttle landed at Kennedy Space Center, back home after more than 700 days in space.

"Sometimes when the train goes past it makes a loud noise but it was nowhere near as loud as that boom this morning," Brevard residents Rich and Carol McCormick said. 

The Port Saint John couple heard the sonic boom Sunday morning from the military space plane known as the X-37B.

The robotically-operated craft is just 29 feet long, one-quarter the size of a shuttle.

The mini-shuttle carried a classified military payload. It launched back in 2015. 

When it landed, residents from the Orlando area to Brevard County reported experiencing the sonic boom, a phenomenon that occurs when a vehicle flies overhead at faster than the speed of sound. 

Sonic booms were quite common during the space shuttle era.

"I kept looking for a vapor trail because we know about where to look for those," Rich said. "But there was no vapor trail yet -- that kind of shake and that sound we heard made us think there was a launch."

While the purpose of the space plane is classified, some suspect the unmanned, robotically-controlled vehicle was used to spy.

Others believe the maneuverable spacecraft helped ensure America had access to space in case of an attack on U.S. satellites.