Minimum Equipment List

The Minimum Equipment List (MEL) is a document approved by the aviation authority that specifies which aircraft instruments, equipment, or systems may be inoperative at the time of dispatch while still maintaining an acceptable level of safety. The MEL allows aircraft to continue operating with certain deficiencies rather than being grounded until every system is fully functional.

The MEL is derived from the manufacturer's Master Minimum Equipment List (MMEL) but is customized by each operator to reflect their specific operations. Each MEL entry includes:

• The item and its ATA chapter number
• Number installed vs. number required for dispatch
• Operational and maintenance procedures required
• Repair interval category (A: per flight crew assessment, B: 3 days, C: 10 days, D: 120 days)

Some items are never allowed to be inoperative — these are flagged as "go/no-go" items. Examples include fire detection systems, emergency exits, and primary flight instruments. The MEL is a key tool for operational flexibility but requires careful judgment from pilots and dispatchers to ensure safe operations.