When is an aircraft annual inspection due?

Per FAR 91.409(a), an aircraft annual inspection is due every 12 calendar months. The aircraft may be operated through the last day of the 12th month following the previous annual.

When is a 100-hour inspection required?

Per FAR 91.409(b), a 100-hour inspection is required for aircraft used to carry persons for hire (other than as a crewmember) or for flight instruction for hire. The 100 hours is measured by tach or Hobbs time-in-service per the manufacturer's recommendation; the inspection may be exceeded by up to 10 hours en route to the inspection location.

How often do transponders need to be tested?

Per FAR 91.413, transponders must be inspected every 24 calendar months for IFR or VFR operations in airspace requiring a transponder.

How often must the pitot-static system be tested?

Per FAR 91.411, the static pressure system, altimeter, and altitude reporting system must be tested and inspected every 24 calendar months for IFR operations in controlled airspace.

How often does the ELT need to be inspected?

Per FAR 91.207, the ELT must be inspected within 12 calendar months of the previous inspection. Battery replacement is required when the transmitter has been used for more than 1 cumulative hour, or when 50% of the battery's useful life has expired.

Free tool

Aircraft Inspection Due-Date Calculator

Enter your aircraft Hobbs and last-completed dates. See exactly which inspections are overdue or coming due — annual, 100-hour, ELT, transponder, and pitot-static.

Aircraft

Tail number (optional)

Current Hobbs

Hobbs at last 100-hr

100-hour inspections only apply to aircraft used for instruction or hire.

Last completed dates

Annual inspection

ELT battery / inspection

Transponder check

Pitot-static / altimeter / encoder

Status

Enter dates to see results

Annual inspection

Required every 12 calendar months

FAR 91.409(a)

—

ELT battery / inspection

Battery replacement at 1/2 useful life or 1 hour cumulative use; inspect every 12 months

FAR 91.207

—

Transponder check

Required every 24 calendar months

FAR 91.413

—

Pitot-static / altimeter / encoder

Required every 24 calendar months for IFR operations

FAR 91.411

—

100-hour inspection

Required for aircraft used for hire (instruction or charter)

FAR 91.409(b)

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Quick reference

InspectionInterval

Annual inspection

FAR 91.409(a)

Every 12 calendar months

100-hour inspection

FAR 91.409(b)

Every 100 hours of time-in-service (for-hire / instruction)

ELT inspection

FAR 91.207

Every 12 calendar months

Transponder

FAR 91.413

Every 24 calendar months

Pitot-static / altimeter / encoder

FAR 91.411

Every 24 calendar months (IFR)

VOR check (IFR)

FAR 91.171

Every 30 days

Always confirm against your aircraft maintenance records and FAR/AIM. AD compliance and equipment-specific manufacturer requirements vary per aircraft and are not covered here.

Why a free calculator?

Missed inspections happen. Annuals slip. The 100-hour creeps up faster than you remember. ELT batteries quietly age out. Aloft360 was built around this problem — we surface every due-date 30 days out and ground aircraft automatically when an inspection lapses.

This calculator is a simple, no-account version of the same logic — accurate to the FARs, free to use, and yours forever. If you want it running automatically across your fleet without re-entering dates, try Aloft360 free for 30 days.