Friday practice ahead of the Chinese Grand Prix had to be abandoned as mist grounded the medical helicopter.
Poor visibility in Shanghai made landing at the designated hospital impossible, prompting officials to call off the sessions on safety grounds.
FP1 was initially red flagged after only 10 cars had completed or started an installation lap, the action resuming following a 40-minute delay.
Red Bull's Max Verstappen then went quickest but was one of only 14 drivers to set a time, while FP2 was completely written off.
With weather conditions expected to be poor once again on Sunday, there is some speculation that qualifying and the race could be staged on Saturday.