NEWARK, NJ — JetBlue cancelled nearly three-fourths of all scheduled flights across the country yesterday — most in the New York area — because of a winter storm on the East Coast.Aiming to avoid criticism about persistent delays and problems that followed a storm last month, the discount airline had cancelled about 400 of its 550 flights by mid-afternoon.

“It’s a strategic move to cancel your flights in advance to help you position aircraft and crews for a quick recovery when the storm is over,” JetBlue spokesman Todd Burke said.

Other airlines — including American, United, Delta and Continental — also cancelled flights. Outside of New York’s airports, delays or cancellations were reported at airports in Philadelphia, Pittsburgh, Albany, NY, and Boston.

The storm was blamed for at least two deaths in traffic accidents in Pennsylvania. It also forced school cancellations throughout the Northeast and prompted some government agencies to send workers home early.

JetBlue has been under pressure to do better in bad weather since passengers were stranded in planes at John F. Kennedy International Airport for up to 10[1/2] hours during a storm last month. JetBlue was unable to resume normal operations for days afterward because flight crews weren’t where they were supposed to be.

Most of the JetBlue customers in the New York area were notified of yesterday’s cancellations in advance, except for Newark Liberty International Airport, Burke said. He said, “Newark is an unusual circumstance where we had last-minute cancellations.”

Steve Coleman, a spokesman for the Port Authority of New York and New Jersey, which operates the airports, said the Port Authority deployed extra customer service agents to Newark to assist passengers with their cancelled flights. Many customers, though, fumed as they tried to rebook tickets.

At Newark, Karen Opdyke, 48, was trying to get to Miami for a cruise with her husband, three young children and mother after their 9 a.m. flight was cancelled.

“We got on the plane, we got off the plane. We got on the plane and off the plane,” Opdyke said.

As she balanced a crying child next to a pile of luggage, she said she couldn’t book another flight and JetBlue agents were not able to help them book on another airline. “There’s nothing available all week,” Opdyke said.

Overall, about 1,000 flights were cancelled at New York-area airports by mid-afternoon.