Delta Air Lines warns of rocky July 4 travel weekend

Delta Air Lines has issued a systemwide waiver for travelers to rebook at no charge July 1-4, a sign that there is likely to be mass cancellations this holiday weekend.

• Last weekend, Delta, the dominant carrier at Minneapolis-St. Paul International Airport, canceled more than 600 flights and delayed more than 2,000.

How it works: Travelers can rebook on delta.com for anytime between now and July 8 without paying a fee or fare difference.

State of play: The core issue, writes Thrifty Traveler's Kyle Potter, is that Delta is experiencing a pilot shortage. Delta pilots wrote an open letter last month raising alarm about working excess overtime hours to keep the airline running.

What's ahead: The Delta pilots will be picketing at MSP Airport Thursday as part of a nationwide effort by their union to get a better contract from the airline, writes Axios Atlanta's Emma Hurt.

• Of note: Because the pilots — members of the Delta unit of the Air Line Pilots Association — are picketing on their days off, service will not be affected.