Even at 5:30 a.m., passengers were wide awake as they waited to board Tuesday morning’s nonstop from Pittsburgh to Atlanta on Delta Air Lines.

Waiting at Gate D76 inside Pittsburgh International Airport’s Airside Terminal, travelers chatted with one another and took photos of the unique aircraft parked outside: a McDonnell Douglas MD-88 aircraft about to carry passengers for the last time.

The flight signified the end of an era for Delta, aviation enthusiasts and the entire aviation industry, as the Atlanta-based carrier officially retired the remainder of its MD-88 and MD-90 fleets on Tuesday.

Delta was the last U.S. airline to fly aircraft in the MD-80 family, after American, Alaska Airlines, Allegiant and Spirit, among other airlines, phased out the aircraft in recent years. Commonly referred to as a “workhorse” for the industry, the long-bodied plane is admired by pilots and aviation enthusiasts alike for features including a traditional analog cockpit and pair of noisy Pratt & Whitney JT8D turbofan engines.

Five other airports also waved farewell to MD-88 flights on Tuesday. Many of the passengers who booked a seat on Delta Air Lines flight DL2375 out of PIT traveled from across the country just to take part.

Michael Evans, an executive recruiter from Chicago, fell in love with the plane as soon as it started flying.

“I remember when the MD-88 came out and replaced the [Boeing] 727,” recalled Evans, who traveled from Chicago O’Hare on Monday to catch Tuesday’s flight to Atlanta. “With the analog cockpit and the sound of the engines, it’s just an incredible flying experience. It’s really the last aircraft that has some of the romance of flying – these are the aircraft where every input is done by the pilot.”

Similarly, a pair of friends, Gregg Pullano and Brian Szemon, traveled to PIT from Cleveland to experience one last flight on the aircraft fondly referred to as the “Mad Dog.”

“It has a classic design,” noted Pullano. “It’s the last one to have those old-school, loud turbofan engines, high-powered takeoff. It’s fun to watch and it’s fun to fly.”

“You just don’t feel that with modern aircraft,” Szemon added. “They don’t throw you back in the seat – the modern aircraft are really gentle now. This [MD-88] is like full thrust, back of the seat.”

For others on board Tuesday morning, the aircraft held a more personal significance.

Chris Portman, a PIT-based customer service representative for Delta and his wife, former Delta employee Emilia Portman, had a special reason to catch the MD-88 flight with their two young daughters.

“For our first date we went on this flight,” Chris Portman explained.

Another aviation enthusiast, Brent Mooney, traveled from Atlanta to Pittsburgh for the flight, well, back to Atlanta.

“This is my childhood route,” said Mooney. “I have family in Pittsburgh and I’ve flown this route so many times on this exact aircraft. I chose to take this flight because it means a lot to me.”

Delta began flying its MD-88 aircraft in 1987 and the MD-90s in 1995. Over three decades, the carrier owned 120 MD-88s and 65 MD-90s. In total, Delta’s “Mad Dogs” have carried roughly 750 million passengers over more than 600 combined routes.

On Tuesday morning, the final MD-88 flights departed for Atlanta from Bradley International Airport in Windsor Locks, Connecticut; Sarasota-Bradenton International Airport in Florida; Virginia’s Richmond International and Norfolk International airports’ Raleigh-Durham International in North Carolina; and Washington Dulles International Airport.

The last MD-88 flight arrived in Atlanta from Washington Dulles and the last MD-90 flight arrived from George Bush Intercontinental Airport in Houston. Flight DL2375 from Pittsburgh marked the second-to last passenger flight on Delta’s MD-88. Ultimately, the planes will retire to an aircraft boneyard located in Blytheville at Arkansas International Airport.

View more photos from the departure here.