PC24 Captain reported receiving a FLAP FAIL CAS message during arrival descent. The crew diverted to an airport with a longer runway.

Narrative

While in the descent into ZZZ on a repositioning flight; descending out of FL180 doing 280 knots the flaps synoptic went amber followed by an amber FLAP FAIL CAS (appeared to be 0°). We asked approach to level at 10;000 feet to work an issue. We ran the QRH; determined we needed to divert to a suitable airport with a long runway. After completing the QRH; getting new Vref speeds; landing distance; and good weather; we decided on diverting to ZZZ1. ATC was notified and a clearance to ZZZ1 was given. We flew no faster than 200 knots per the QRH. Operations was also notified. The PF; who was SIC on this flight (PIC qualified line Captain); recently went through recurrent training and was instructed a flaps failure is a flight control; so [priority handling] was needed. We [requested priority handling]; and landed runway XX at ZZZ1 normally (no heavy braking needed) with a normal taxi to the FBO. Airport operations followed up with us and the aircraft was written up and maintenance was notified.