(Image source from: USA Today)

Parts of Terminal 4 at Phoenix Sky Harbor International Airport were reopened Sunday morning after a multi-hour closing, prompted by a leery abandoned rental car, snarled air traffic and led to the cancellation of numerous flights.

The airport was wholly open at about 11:15 a.m. local time (2:15 p.m. ET) after Phoenix police ascertained the car was not a menace.

Phoenix police officers at the airport spotted the unaccompanied rental car on the curb line of the upper deck of Terminal 4 at about 7 a.m. The bomb squad was then called out to determine whether the car was really a threat.

Sgt. Tommy Thompson, a Phoenix police spokesman, said investigators were still checking the vehicle at 11 a.m.

"It's a lengthy process," he said in a press conference.

Police had still to identify the car owner.

A spokesman for the airport Gregory Roybal encouraged travelers to confirm the status of flights with their airlines. 

The terminal's east side, before the security checkpoints, had been evacuated for about three hours Sunday morning. Three of the four security checkpoints were shut, and the PHX Sky Train was not dropping off passengers at Terminal 4. 

According to Flight-tracking website FlightAware, hundreds of flights had been delayed Sunday, either in leaving or in arriving at Sky Harbor. The site showed about 30 canceled flights, largely on Southwest Airlines.

Volunteers at the airport brought therapy dogs to assist calm the flourishing crowd.

By noon, passengers were taking about 25 minutes to get through security and into Terminal 4, though lines were closed concisely as the system was so crowded with passengers. 

Security checks at the terminal were being accelerated - with passengers leaving their shoes on and their bags closed, simply emptying their pockets and moving quickly through the checkpoint.

By Sowmya Sangam