Mission 4 scramble wait time?

[Spudknocker]

How long is the wait time till the order to scramble in mission 4? Is there a certain radio button I'm supposed to be on to get the message? Wanted to make sure I'm not missing anything, would be nice if the briefing told the player how long the wait is so we don't think we've missed something

[Wags]

As per the mission brief, it is signaled by the red flares at almost the start of the mission.