in august 1990, ang f-15 and f-16 fighter units initiated similar rotational service for operation coronet nighthawk, the successor to operation volant oak, out of howard air force base, panama. those units monitored suspected airborne drug traffickers transiting central america as well as the adjacent oceans. as the 1999 transfer of the panama canal to panama approached, the air national guard began turning the operation over to civilian contractors. the last air national guardsmen completed their deployments to these south american sites in 1999.