Sondre is normally open 1100-2000 UTC Monday-Saturday. Therefore, it is typically closed for eastbound flights and westbound flights on Sunday. The only time I have used it as an ETP airport is when regulations required its use due to 60 minute ops (partial nav failure prior to entering tracks westbound). In the case of 60-minute ops, there are no exceptions (as in 120 ETOPS)...you must continuously remain within 60 minute arcs, and Sondre was the only way to comply with this.