Tracked live by the FAA, but its flight plan was first seen after takeoff, so we don't know the scheduled time and can't say whether it's late.

FRONTIER · FLIGHT F9 1923 LANDED 3:56 PM PT, ~4 MIN LATE · SCHEDULED TIME UNKNOWN
Yesterday

F9 1923 · LAS → ONT

took off 3:19 PM PT · landed 3:56 PM PT (scheduled time unknown)
Forecast issued Sat 10:00 PM ET · 4h after departure

Odds over time

Arrive at ONT more than 15 minutes late?
39% chance · ±0 pts – · 24h
HOW SURE WE ARE Very high. The odds now come almost entirely from live conditions.
LIVE IN THE AIR 0% 15% 30% 45% 60% 3h Departs