The busy summer travel season is underway, and United Airlines is expecting more than 6 million travelers over the July Fourth holiday—up about half a million from last year.

At Newark Airport, construction has improved, but concerns remain about technology and air traffic control.

United's chief pilot at Newark, Dave Weiselberg, says they're ready, though weather remains the top concern.

He says a series of storms can create a snowball effect that disrupts operations.