Originally Posted by
hitchens97
...Also which one is the International default?...
ICAO DOC4444 PANS-ATM (Air Traffic Management) states*:
7.10 CONTROL OF ARRIVING AIRCRAFT
7.10.1 Separation of landing aircraft and preceding landing and departing aircraft using the same runway
Except as provided in... Chapter 5, Section 5.8, a landing aircraft will not normally be permitted to cross the runway threshold on its final approach until the preceding departing aircraft has crossed the end of the runway-in-use, or has started a turn, or until all preceding landing aircraft are clear of the runway-in-use.
Note 1.— See Figure 7-2.
Note 2.— Wake turbulence categories and groups are contained in Chapter 4, Section 4.9 and time-based wake turbulence longitudinal separation minima are contained in Chapter 5, Section 5.8.
Note 3.— See 7.6.3.1.2.2.
7.10.2 Clearance to land
An aircraft may be cleared to land when there is reasonable assurance that the separation in 7.10.1 ...will exist when the aircraft crosses the runway threshold, provided that a clearance to land shall not be issued until a preceding landing aircraft has crossed the runway threshold. To reduce the potential for misunderstanding, the landing clearance shall include the designator of the landing runway.
My interpretation of the above is that the ICAO SARPs seem to be more in the spirit of the European/UK attitude to issuing landing clearances, however in my (limited) searching I can't find anything that expressly prohibits issuing a landing clearance to an aircraft a reasonable distance from the threshold while only departing traffic is obstructing the runway ahead of them (the apparent "US" practice).
*I've omitted references to exceptions for gin-clear pre-approved exemptions to these rules...