Her asthma has 'flared up' again. [=her asthma has become suddenly active or worse again]
When the crew saw 'flares', they knew the other ship was in trouble.
The fire is smoldering and there is still a danger of 'flare-ups'.
(..) Major, you better take a look at this. Blain's body, it's gone. It came in through the tripwires. Took it right out from under our noses. That boar had to set off the trip flare, Major, cos there ain't no other tracks. How could anyone get through this and carry out Blain without us knowing it? (..)1987 Predator