Is AD 90-21-17 a recurring Airworthiness Directive?

No — AD 90-21-17 is a one-time directive. Verify it was complied with in the aircraft's records.

Which aircraft does AD 90-21-17 apply to?

AD 90-21-17 applies to Boeing — models 747. Serial/part conditions may narrow it to specific aircraft.

Airworthiness Directive 90-21-17

one-time

AD 90-21-17 · 1990-01-01 · airframe

Airworthiness Directives; instrument. B. On airplanes which have been modified to the stretched-upper-deck configuration, as identified in Boeing Alert Serv

Which aircraft AD 90-21-17 applies to

MakesBoeing

Models747

applicability read from the AD teaser — confirm exact model/serial from the records

Whether AD 90-21-17 actually applies to your aircraft (by serial and installed parts) and whether it’s already complied with comes from that aircraft’s records.

Supersession

Superseded by AD 2012-10-03 — comply with the superseding directive.

How AD compliance is recorded

A valid compliance record (14 CFR 43.9) states:

Method of compliance — The specific action taken (inspected, replaced, modified) and to what revision.

Date — When the work was done.

Aircraft time — Total time in service / tach at compliance — how recurring next-due is computed.

Signature & certificate — The A&P/IA who returned it to service, with certificate number.

Is AD 90-21-17 complied with on your aircraft?

Tailplate reads a tail number’s logbooks and matches every applicable AD — including this one — to its compliance evidence, with recurring next-due dates computed.

Look up a tail number →

Applicability is derived from the FAA directive corpus and is advisory, not a legal airworthiness determination. Compliance is established only from an aircraft’s actual records.