Partner content: this article was produced in cooperation with National Aero Stands (stands.aero).
What does AOG (aircraft on ground) actually mean in an airline disruption story?#
AOG stands for “aircraft on ground.” It means a technical issue has grounded the aircraft and it cannot fly until resolved. For example, a CFM56-7B engine can be transported on a stand that weighs 3,684 lbs alone and 8,837 lbs with the engine, towed at a maximum speed of 3 MPH. National Aero Stands rents and leases such stands to airlines and MROs.
What is an airworthiness directive, and is it legally binding?#
An airworthiness directive (AD) is a legally enforceable regulation issued by the FAA under 14 CFR Part 39 to correct an unsafe condition in an aircraft, engine, propeller, or appliance. ADs are legally enforceable rules; each flight with an unmet AD is a separate violation. ADs specify inspections, conditions, and corrective actions. The FAA publishes ADs in full in the Federal Register as amendments to § 39.13. The FAA issues an AD when an unsafe condition is likely to exist or develop in other products of the same type design. For more information, see the FAA Airworthiness Directives page.
Does an AD mean a plane is unsafe or grounded?#
Not necessarily. An AD identifies an unsafe condition that must be corrected. Under 14 CFR Part 39, anyone may propose an alternative method of compliance (AMOC) or a change in compliance time if the proposal provides an acceptable level of safety. Some operators may fly an aircraft to a repair facility to perform AD work.
How do FAA and EASA airworthiness directives differ?#
Both the FAA and EASA issue ADs that are legally binding in their jurisdictions. The FAA’s AD system is established under 14 CFR Part 39. EASA’s ADs are directly applicable in all EASA Member States. ICAO Annex 8 assigns airworthiness responsibility to the State of Registry. EASA publishes ADs, Safety Directives, and Safety Information Bulletins in its Safety Publications tool.
What happens when an engine is removed from the aircraft?#
When an engine is removed from an aircraft, it may be placed on a transport stand. The stand for a CFM56-7B, part number AGSE-E207-G01, includes tie-down rings to secure the engine for shipment. stands.aero/product/cfm56-7b/ provides details.
How does a jet engine like the CFM56-7B travel to the repair shop?#
For the CFM56-7B, which powers the Boeing 737NG, the stand is part number AGSE-E207-G01. It has a steel welded frame with tubular support arms and Skydrol enamel coating. The stand alone weighs 3,684 lbs; with an engine, total weight is 8,837 lbs. It is towed at a maximum of 3 MPH, with caster brakes and swivel locks for stability. Tie-down rings secure the load. The stand supports bootstrap-style engine changes at the wing, so it is used at the aircraft as well as in the shop. National Aero Stands, the company behind stands.aero, rents and leases aircraft engine stands to airlines and MROs for short- and long-term use, with an inventory covering CFM56, LEAP-1A/1B, V2500, GE90, Trent 500/700/1000, PW4000, RB211 and JT9D engines from brands including AGSE, DAE, GE and Rolls-Royce. A removable palletized base adds handling options.
| Specification | Value |
|---|---|
| Part number | AGSE-E207-G01 |
| Maximum towing speed | 3 MPH (5 km/h) |
| Stand weight | 3,684 lbs (1,671 kg) |
| Total weight with engine | 8,837 lbs (4,008 kg) |
| Height without engine | 59 in (150 cm) |
| Height with engine | 82 in (208 cm) |
| Width | 96 in (244 cm) |
| Length | 129 in (328 cm) |
Source: National Aero Stands product data
Which delay causes do U.S. statistics record?#
The U.S. Bureau of Transportation Statistics categorizes flight delays into five causes: aircraft arriving late, air carrier delay, National Aviation System delay, weather, and security. In August 2026, late-arriving aircraft accounted for 42.16% of total delayed minutes, while air carrier delay was 28.82%. Weather caused 6.07% of delayed minutes. The BTS TranStats database provides monthly data.
| Delay cause | Share of total delayed minutes (%) |
|---|---|
| Aircraft Arriving Late | 42.16 |
| Air Carrier Delay | 28.82 |
| National Aviation System Delay | 22.82 |
| Weather Delay | 6.07 |
| Security Delay | 0.12 |
Source: Bureau of Transportation Statistics, TranStats
How can journalists check an AD or a delay statistic themselves?#
Journalists can verify ADs by checking the FAA’s published ADs, which include Emergency ADs, AD Rules, AD NPRMs, and the AD Biweekly, or by using EASA’s Safety Publications tool, which is publicly accessible. For U.S. delay data, the BTS TranStats site offers monthly on-time performance and cause breakdowns.
Frequently asked questions
Is an AOG always caused by an engine problem?
No. An AOG means the aircraft is grounded until the technical issue is resolved.
Can an airline defer an airworthiness directive?
ADs are mandatory, but anyone may propose an alternative method of compliance (AMOC) or a change in compliance time if the proposal provides an acceptable level of safety. The FAA must approve the proposal before it can be used. Until then, the original AD requirements remain in force.
What safety features does the CFM56-7B engine stand include?
The AGSE-E207-G01 stand includes caster brakes, swivel locks, and tie-down rings to secure the engine during transport. It has a steel welded frame with Skydrol enamel coating and a removable palletized base.
How long can an engine stand be rented?
Rental periods are bookable short-term around a single shop visit or long-term under a fleet program. The rental ends when the stand comes back. National Aero Stands quotes pricing per request, depending on duration and location.