VANCOUVER - A passenger aboard a flight from Vancouver to Chicago says there were some tense moments as the pilot swerved to avoid crashing into a smaller aircraft.

Callum Snape was flying on a United Airlines plane on Monday afternoon when he felt the right wing drop and the aircraft do a hard right turn before speeding up.

“I was definitely panicking because I knew whatever happened wasn't meant to happen,” he said.

The Vancouver-based photographer was seated in an aisle near the back of the aircraft, where there were no windows. Without being able to see outside, he worried something had happened to the plane's engine.

“I've been in really bad turbulence and nothing's happened like that before,” he said Tuesday.

Other passengers seemed equally startled by the sudden movement.

“They shrieked initially but there was no screaming and no one was really uncomfortable. But it definitely got people edgy and clinging to their seats,” Snape said.

The 737 touched down at Chicago's airport about 15 minutes later and the pilot announced the plane had narrowly missed a smaller aircraft that did not have navigation equipment onboard.

“Then everyone started clapping and was really happy,” Snape said.

The American Federal Aviation Administration said in a statement that the pilot reported seeing a glider near Rockford, Ill., about 120 kilometres from Chicago's airport.

Gliders are light and motorless and use gravity and air currents to fly.

The two aircraft did not make contact, the aviation agency said, adding the United Airlines plane climbed nearly 122 metres. It's now investigating what happened.

United Airlines said in a statement the flight landed safely “and all passengers deplaned normally after the pilots were required to deviate from the aircraft's normal flight path because they spotted a glider.”

The airline said it is following up with air traffic control to do a complete review of what happened.

While some passengers may have been left shaken, Snape said he doesn't have any concerns about taking to the skies again.

“I'm really, really confident about flying,” he said.