Not every emergency is a distress. In aviation, we distinguish between distress (grave and imminent danger) and urgency (serious concern, but the aircraft is not yet in immediate danger and does not require rescue services to stand by).
An urgency situation is:
  • Engine problem but you can still fly: rough running, but still making altitude
  • Single-engine aircraft with a partial power loss but can reach an aerodrome
  • Hydraulic system malfunction, but flight control surfaces still respond
  • Electrical system failure, but you are within glide range of a suitable field
  • Medical emergency (passenger illness, injury) that requires urgent but not emergency landing
  • Minimum fuel: you can still reach an aerodrome, but with very limited reserves
  • Weather deterioration below landing minima at destination, but you can divert to an alternate
In these cases, you transmit PAN-PAN (from the French "panne" meaning breakdown) instead of MAYDAY. PAN-PAN receives urgent handling—ATC will clear traffic and prioritize you—but it does not trigger full emergency services mobilization.
The format for PAN-PAN is identical to MAYDAY, except you say PAN-PAN three times instead of MAYDAY:

Urgency - Hydraulic Malfunction

Basel Approach · D-ABCD

PILOT: PAN-PAN PAN-PAN PAN-PAN, Basel Approach, D-ABCD
PILOT: Hydraulic system malfunction, flight controls normal, requesting priority landing Zurich
PILOT: Position, 15 miles northeast of Basel, altitude 3000 feet, two on board
ATC will respond to a PAN-PAN with urgency, but their response pattern differs from distress. They will typically:
  • Advise you of the nearest suitable aerodrome
  • Provide direct routing and descent clearance /li>
  • Arrange for you to land ahead of other traffic
  • Have ground rescue standing by (but not full emergency services unless you later declare MAYDAY)
The critical distinction: declare MAYDAY if you believe your aircraft or occupants are in grave and imminent danger. Declare PAN-PAN if serious but not yet life-threatening.