From my apartment window overlooking southwest Utah County observed two orange/yellow fireballs about five minutes apart slowly ascending in the sky. My girlfriend and I observed the same type of object a few days previously about 40 miles away in West Valley City (flying over Valley Fair Mall).
Both fireballs seemed to originate from close to ground-level starting above the city of Palmyra, Utah (appx. 40.148832,-111.719799). They ascended gradually in the air at roughly a 35 degree angle. I'm guessing the objects were 10-20 feet in diameter.
The first object headed due north and reached an altitude of approximately 10-15,000 feet (slightly higher than half the altitude of commercial jets that frequently fly above the path of the these two objects). After approximately two minutes I lost sight of the first object as it passed behind trees a few yards from my balcony.
The second object seemed to arise from the same area traveling somewhat north, northeast. It flew for about 3/4 of the distance as the first object but abruptly faded and vanished.
I would estimate their speed to be faster than a twin-engine plane or transport military helicopter, but traveled about as fast as the life-flight helicopter which frequently flies in the same area to and from Utah Valley Regional Medical Center.
I was able to record the object with a Sony DCR-TRV11 digital video camera. The objects looked to be active balls of flame changing colors from orange to yellow. There were no blinking lights and no other observable lights coming from the object.