Currently, any armed PHALANX aircraft may be ordered to intercept a flying UFO (provided it can be reached), and any manned PHALANX transport may be ordered to secure a ground site.

Any PHALANX craft could also be ordered to follow a flying UFO (provided it can be reached).


As I see things, this could be done by:
# Ordering to close the target as if an interception
# When close, staying out of range of the UFO weapons (plus a margin?) and matching its speed if the PHALANX craft is faster.
In case the UFO is faster or becomes faster, the Follow could switch to Intercept (#1), or the order would be canceled and the craft return to base.

This way, an UFO could be followed until it openly lands (creating a ground mission) or it disappears (either flying to orbit or down to a base)