When Able
When used in conjunction with ATC instructions, gives the pilot
the latitude to delay compliance until a condition or event has
been reconciled. Unlike "pilot discretion," when instructions are
prefaced "when able," the pilot is expected to seek the first
opportunity to comply. Once a maneuver has been initiated, the
pilot is expected to continue until the specifications of the
instructions have been met. "When able," should not be used when
expeditious compliance is required.