Father, son among 4 on board missing aircraft The plane dropped off the radar at 10:30 a.m. Thursday, according to CAP.

 -- A search and rescue is underway after a single-engine Piper aircraft with four people on board went missing after departing Grand Junction, Colorado, around 10 a.m. local time Thursday, officials said.

Teams from the Civil Air Patrol, an auxiliary of the U.S. Air Force leading the search efforts, have picked up a signal from an emergency beacon, known as an ELT, coming from an area near Dove Creek that they believe is coming from the missing aircraft.

Members of the CAP National Radar Analysis team were able to use transmitter and radar data to conclude that the aircraft dropped off radar at 10:30 a.m. Thursday.

Air Crews from multiple CAP bases were dispatched Friday morning but were forced to turn back to due snowy conditions in the area. Two ground crews from Colorado are moving into the search area.

The Federal Aviation Administration confirmed that the aircraft was missing and issued an alert.

Jon Kaupp, the son of pilot Bill Kaupp, told ABC News that his 65-year-old father was planning to fly another son, 28-year-old Clint Kaupp, and their respective best friends west over Moab, Utah, before turning south to their destination of Albuquerque, New Mexico. The other passengers were Tim Mueller, 28, and Ron McKenzie, 66, according to Jon Kaupp.

It's unclear if Bill Kaupp was familiar with that area of Colorado and Utah.

There were light snow and mist in Grand Junction Thursday morning but no significant storms, according to ABC News meteorologists.