Delta Air Lines has faced significant challenges recently, leading to the cancellation of hundreds of flights early Tuesday morning.

The issues, which began last week, have persisted into a fifth day and are expected to continue through the end of the week.

This situation has affected an estimated half a million people, disrupted holidays and travel plans, and prompted a federal investigation.

As of 2 PM ET, Delta had canceled 466 flights, and its regional carrier, Endeavor Air, had canceled another 28 flights.

These cancellations follow more than 4,500 flights canceled between Friday and Sunday.

Additionally, over 1,000 Delta and Delta Connection flights were listed as delayed.

The canceled flights by these two carriers represented nearly 70% of all flights within, to, or from the United States that were canceled on Monday.

Transportation Secretary Pete Buttigieg announced that the Department of Transportation would investigate to ensure Delta is following the law and treating passengers fairly.

He expressed concerns about passengers being on hold for hours, sleeping on airport floors, and unaccompanied minors being stranded.

The DOT has received a high volume of consumer complaints about Delta's actions since Friday.

Delta's problems stemmed from a software update issued late Thursday night that crashed Windows software, causing a cascade effect throughout the global airline industry.

While most airlines recovered by the end of the weekend, Delta has been unable to fix the issue, leaving it unable to find the pilots and flight attendants needed to fly its planes.

The problems are expected to continue for at least a few more days.

Delta is offering premium pay and additional assurances to its crew members to help fix its staffing problems.

However, the service meltdown has already cost Delta about $163 million through Monday, with additional costs expected.

The meltdown has damaged Delta's reputation for on-time performance and customer service, which will take time to repair.

Passengers have faced significant disruptions, with many stranded and unable to return home.

Some have booked other flights that were subsequently canceled, and a lack of hotel rooms has forced many to sleep in airports.

Delta crew members are also dealing with similar frustrations, with some unable to get hotel rooms and sleeping at airports.

Delta's service issues have also caused it to lose future bookings from frustrated customers.

The past weekend was the busiest travel period of the summer, with 90% of seats booked, making it difficult for Delta to find other flights for affected customers.

Reuniting passengers with their checked baggage will take many more days.

United Airlines was also affected by the computer problem, with more than 1,000 canceled flights.

However, it was back to near-normal operations on Monday.

At Atlanta's Hartsfield-Jackson International Airport, Delta's headquarters and largest hub, thousands of pieces of luggage are lined up on the floors of baggage claim, waiting to be reunited with their owners.

Delta employees from various departments are supplementing efforts to help passengers find their bags.

The service meltdown will cost Delta both in terms of its reputation and financial losses.