Both stars saw the private jet crash and burst into flames as it attempted to land at the airport, which is a main destination for celebrity skiing fans.
Country singer Rimes, who was holidaying with her husband Eddie Cibrian, took to Twitter.com minutes after the crash and wrote, "So sad. Horrible plane crash we just saw happen at the Aspen airport."
Nealon has added, "Horrible plane crash here at Aspen airport. Exploded into flames as it was landing... Fire trucks and other emergency vehicles still at scene. No word on survivors or who was on jet but I can't imagine there are survivors."
In fact one person was killed and two injured in the accident.
The Weeds star later added, "Airport is closed now. I think I'll drive back to La after seeing that."
A Federal Aviation Administration (Faa) spokesman has confirmed the Bombardier Challenger 600 plane crashed while attempting to land.