Delta flight returns to Atlanta due to cabin pressurization issue

ATLANTA - A Delta Air Lines flight bound for Kansas City, Missouri, returned to Atlanta on Wednesday evening. 

The flight crew observed a cabin pressurization issue, the airline said.

What we know:

Delta Flight 1660, a Boeing 737-900ER, departed Hartsfield-Jackson Atlanta International Airport at 6:54 p.m. before turning back. 

It landed safely at 8:13 p.m., according to a Delta spokesperson. 

Oxygen masks did not deploy in the cabin.

The flight was carrying 177 passengers, two pilots, and four flight attendants. 

Maintenance crews are inspecting the aircraft, while airport staff provided meals, beverages, and snacks for affected passengers. 

What we don't know:

The cause of the pressurization issue remains under investigation.

What's next:

Delta said a replacement aircraft was scheduled to continue the flight later in the evening.