If ATC gives vectors to number 2 before he is cleared off by number 1, what must he do?

When ATC provides vectors to the second aircraft in a formation before the first aircraft has been cleared off, the correct procedure is that the second aircraft must continue to maintain its position with respect to the first aircraft until receiving the proper clearance to depart from that position. This protocol ensures safety and maintains the integrity of the formation, as any premature maneuvering by number 2 could lead to a dangerous situation where the two aircraft might lose their spacing or conflict with each other.

Following this procedure emphasizes the importance of clear communication and adherence to air traffic control instructions in formation flying. The second aircraft must wait for the explicit clearance of number 1 to ensure that both pilots are coordinating effectively and flying safely. This approach helps to avoid potential miscommunications or conflicts during the maneuvering process.