UPDATE 8/20: The Big Boy's big move is, once again, delayed.
Officials with the Museum of the American Railroad confirmed to News 8 Tuesday morning the move will again be delayed until at least Saturday due to complications.
EARLIER: IRVING — After several delays, a historic steam locomotive is slowly making its way to Collin County.
"Big Boy" left Dallas on Sunday, being towed along the rails to Irving, where complications left it standing at the downtown Irving station.
Officials hope the steam engine will be back on track Tuesday to its final whistle-stop — the Museum of the American Railroad in Frisco.
Officials are awaiting clearance from the railroad to get Big Boy back on schedule.
"We kind of have to work around a lot of the rail traffic that's here — passenger and freight traffic," said museum CEO Bob LaPrelle.
The top speed of the historic steam engine is just 10 miles per hour — a far cry from the modern trains or even what Big Boy itself was capable of in its heyday.
Its aging bones and its stiff joints reluctantly returned to motion on Sunday for a final 55-mile ride on the rails to a new retirement home at the Museum of the American Railroad in Frisco.
"It was cool. Finally happened. Very cool," said train enthusiast Tim Cate, who came to see the engine off Sunday because his little boy named Daniel has been obsessed with the Big Boy.
"I'm really excited," Daniel said. "It's actually pretty impressive. And I see why they call it the Big Boy... because it's big!"
The 1.2 million pound dynamo — the largest steam engine in the world — was originally fabricated in the 1940s to transport war materials. Moving it from its previous home at Dallas Fair Park to Frisco has been a battle in its own right.
But those who've followed this mammoth effort say seeing an American engineering marvel being towed down the tracks to a place where it will gain new appreciation was worth all the waiting.
Officials hope Big Boy will be back on track by mid-morning Tuesday and the timetable has it arriving in Frisco before nightfall.