Museum of American Railroad officials postponed the move of the Union Pacific “Big Boy” hours before it was to leave Fair Park for Frisco on Sunday. Concerns over how the locomotive would negotiate a wye along the route caused the postponement, according to an email released by MAR.

The museum’s F7A diesel locomotive painted in Santa Fe Warbonnet colors and two storage box cars were moved instead.

No date has been announced when the Big Boy will attempt to be moved again.

After a few previous unsuccessful attempts to move the “Big Boy”, MAR was ready to make the much anticipated move of the vaunted locomotive.Museum officials received word on Friday that the move would begin Sunday. Dallas, Garland and Northeastern Railroad crews, which are assisting on the move, were expected to arrive at Fair Park in Dallas at 7 a.m. today to make preparations.

“It looks like we’re finally going to get it done,” MAR CEO Bob LaPrelle said on Friday.

At least two recent attempts to move the locomotive were thwarted because of heavy traffic and a derailment along the route from Dallas to the museum’s new home in Frisco, TX. Along with DGNO, Burlington Northern Santa Fe and Trinity Railway Express are assisting in the move. DGNO was expected to hand off No. 4018 to BNSF at the Irving yard. From there, BNSF was to take the massive locomotive to Frisco.