I assume that while en route, one aircraft could simply pick up flight following and the others do not need to talk to ATC, but what about upon reaching an airport? Do they simply announce "flight of xxx 10 mi east with W for full stop" and get successive landing clearances, or do they all break apart before getting close to the airport? Thanks!
As long as the aircraft are in formation, they are controlled as a single aircraft.
From US DoT OrderJO 7110.65T ATC General Control:
2-1-13. FORMATION FLIGHTS
a. Control formation flights as a single aircraft. When individual control is requested, issue advisory information which will assist the pilots in attaining separation. When pilot reports indicate separation has been established, issue control instructions as required.
The decision to break the flight lies with the pilot in command, and the ATC then controls the aircraft individually.
Separation responsibility between aircraft within the formation during transition to individual control rests with the pilots concerned until standard separation has been attained.
Upon break-up of the formation flight, the controller initiating the break-up shall ensure that all aircraft or flights are assigned their proper equipment suffix.
Do they simply announce "flight of xxx 10 mi east with W for full stop" and get successive landing clearances, or do they all break apart before getting close to the airport?
It is up to the pilots.
As aeroalias said, formation flights are considered a single aircraft and are controlled as such (although there is additional separation added: either "standard separation plus one mile applied to the lead aircraft" for a standard formation, or "standard separation applied in front of the lead and behind the tail aircraft" for a non-standard formation).
With regards to runway operations (takeoffs and landings):
- A formation flight is cleared for takeoff once. It is up to the pilots to decide whether they take off single-file and join up when airborne, or take off as a group, or two at a time side-by-side, or what. This will depend on the skill and proficiency of the pilots as well as the type of aircraft; a formation of A-10s and a formation of Cherokees will be quite different.
- A formation flight is cleared to land once. Again, responsibility for aircraft safety lies with the flight lead and the rest of the pilots, and they may elect to all land at the same time, or in a line, or successively by virtue of an overhead break maneuver.
The controller is not responsible for spacing the flight elements so as to provide same-runway separation between them unless they begin issuing control instructions to individual elements of the flight.
If the pilots are uncomfortable landing as a flight, they can request to break up and the controller will then issue appropriate instructions to separate the elements of the flight. For an IFR flight this will likely be diverging headings; for a VFR flight it could be direction-of-flight, S-turn, or 360º-for-spacing instructions. Once the elements have broken up the controller will issue individual landing clearances and ensure proper runway separation.
Note that "An aircraft conducting an overhead maneuver is VFR and the IFR flight plan is canceled when the aircraft reaches the “initial point” on the initial approach portion of the maneuver" (7110.65 3–2–10d).