US Airways Express Flight 4321 from Elmira, N.Y., touched down without incident, airline spokesman Todd Lehmacher said. The plane was carrying 34 passengers and three crew members.
An audio recording of the crew's communication with air traffic controllers, which took place around 1:45 p.m., was posted on the website LiveATC.net.
"You said was there a flare being shot up ... at you?" the controller asked.
"Yeah, it probably wasn't more than 50 feet off our right wing," came the reply.
Philadelphia police said they received a 911 call at about 2 p.m. reporting someone had shot off a flare gun at an intersection near the airport. Officers went to the intersection but found no evidence of it, Officer Jillian Russell said.
The incident led officials to close one runway for about 30 minutes, airport spokeswoman Victoria Lupica said.
In March, a plane was forced to abort its landing in Philadelphia after a man breached security and drove an SUV onto the runway.