Passenger Revenue per Available Seat Mile (PRASM): Airline Unit Revenue

Passenger revenue per available seat mile (PRASM) measures passenger revenue generated for each available seat mile of airline capacity.

It is one of the industry's most widely followed unit-revenue metrics because it combines pricing and capacity utilization in a single denominator-normalized measure.

Formula

PRASM = Passenger Revenue ÷ Available Seat Miles

If an airline earns $16 billion of passenger revenue on 100 billion ASMs, PRASM is 16 cents.

PRASM combines yield and load factor

A useful simplified relationship is:

PRASM ≈ Passenger Yield × Passenger Load Factor

Airline Passenger Yield captures passenger revenue per RPM, while Passenger Load Factor captures how much available capacity is filled by revenue traffic.

PRASM therefore can weaken because fares/yield fall, because load factor falls, or because both deteriorate.

PRASM versus total revenue per ASM

PRASM includes passenger revenue only. Total revenue per available seat mile, often called TRASM, uses total operating revenue.

That distinction matters for airlines with material loyalty, cargo, maintenance, credit-card, or other non-passenger revenue streams.

An airline can report stable PRASM while TRASM improves if non-passenger revenue grows faster than capacity.

PRASM is not the same as passenger yield

Yield uses RPM in the denominator. PRASM uses ASM.

If the airline discounts fares enough to fill more seats, yield may decline while load factor rises. The net effect on PRASM depends on the magnitude of each move.

That makes PRASM a useful bridge between pricing and utilization rather than a pure price metric.

Worked example

Suppose an airline reports:

• passenger revenue: $17 billion;
• ASM: 100 billion;
• RPM: 85 billion.

PRASM is:

$17 billion ÷ 100 billion = 17 cents

Passenger yield is:

$17 billion ÷ 85 billion = 20 cents per RPM

Load factor is:

85 ÷ 100 = 85%

And the simplified bridge holds:

20 cents × 85% = 17 cents PRASM

Why PRASM can be hard to compare across airlines

PRASM is affected by network structure and accounting classification. Investors should consider:

• domestic versus international mix;
• premium versus main-cabin mix;
• average stage length;
• regional-carrier arrangements;
• loyalty revenue classification;
• ancillary revenue treatment; and
• capacity growth timing.

Higher PRASM does not automatically mean a more profitable airline because cost structure can differ materially.

PRASM and CASM

PRASM is a revenue-side unit metric. Cost per Available Seat Mile is the cost-side counterpart.

The spread between unit revenue and unit cost can be directionally useful, but it is not a complete operating-margin formula when the revenue and cost numerators have different scopes or when adjusted CASM excludes fuel, special items, or other costs.

What investors should check

1. Did PRASM move because yield, load factor, or both changed?
2. How fast is ASM growing?
3. How does PRASM compare with TRASM?
4. Are premium and loyalty revenues changing mix?
5. Is stage length affecting unit comparisons?
6. Is the comparison reported or adjusted?
7. Is CASM improving or worsening at the same time?

Real-world filing context

American Airlines defines PRASM as passenger revenue divided by ASM. United Airlines reports PRASM alongside yield, load factor, TRASM, and CASM, and Delta analyzes PRASM changes by geographic region with traffic and capacity changes.

Sources:

• American Airlines 2025 Form 10-K
• United Airlines 2025 annual report
• Delta Air Lines 2025 Form 10-K

Bottom line

PRASM measures passenger revenue per unit of airline capacity. It combines pricing and utilization, so investors should decompose changes into yield, load factor, capacity, and mix rather than reading PRASM as a pure pricing signal.

Part of the Airline Operating Model

Connect capacity, traffic, load factor, passenger yield, unit revenue, unit cost, schedule activity, stage length, and fuel efficiency to understand airline economics.

Browse the full operating model in Company Analysis →

Where this concept fits

• Unit revenue and unit costCurrent relationship
  When definitions align, PRASM equals passenger yield multiplied by load factor. CASM puts operating cost on the same ASM denominator, allowing unit revenue and unit cost to be read together without treating either as a complete profit measure.
  Airline Passenger YieldAvailable Seat MilesCost per Available Seat MilePassenger Load FactorPassenger Revenue per Available Seat MileCurrent concept
• Capacity and demand
  Passenger load factor equals RPM divided by ASM. RPM measures paid passenger traffic while ASM measures supplied seat capacity, so the ratio shows how much capacity is being absorbed.
  Available Seat MilesPassenger Load FactorRevenue Passenger Miles
• Schedule activity and fuel economics
  Departures, block hours, and average stage length describe how often and how far the network flies. Fuel gallons consumed and average fuel price per gallon separate fuel volume from fuel price, while available seat miles per gallon relates capacity output to fuel use. These issuer-reported operating statistics add network and fuel context rather than forming a standardized cross-company formula.
  Airline Available Seat Miles per GallonAirline Average Fuel Price per GallonAirline Average Stage LengthAirline Block HoursAirline DeparturesAirline Fuel Gallons Consumed

• Airline Available Seat Miles per Gallon
• Airline Average Fuel Price per Gallon
• Airline Average Stage Length
• Airline Block Hours
• Airline Departures
• Airline Fuel Gallons Consumed
• Airline Passenger Yield
• Available Seat Miles
• Cost per Available Seat Mile
• Passenger Load Factor
• Passenger Revenue per Available Seat MileCurrent concept
• Revenue Passenger Miles

See It in Company Research

These companies are examples of how the concept is reported or discussed in public filings. Definitions can differ by issuer; these links open company research rather than a normalized metric comparison.

• AALOpen operating-model research →8 of 12 reviewed concepts in Airline Operating ModelUnit revenue and unit cost5 of 5 bridge concepts supportedContinue through this bridge:Airline Passenger YieldAvailable Seat MilesCost per Available Seat MilePassenger Load Factor
• DALOpen operating-model research →7 of 12 reviewed concepts in Airline Operating ModelUnit revenue and unit cost4 of 5 bridge concepts supportedContinue through this bridge:Airline Passenger YieldAvailable Seat MilesPassenger Load Factor
• UALOpen operating-model research →9 of 12 reviewed concepts in Airline Operating ModelUnit revenue and unit cost5 of 5 bridge concepts supportedContinue through this bridge:Airline Passenger YieldAvailable Seat MilesCost per Available Seat MilePassenger Load Factor

Explore other companies in this operating model

These companies are linked to at least two other reviewed concepts in the same operating model, but are not currently linked to this concept. This is broader research navigation, not evidence that the company reports an equivalent metric.

• ALGT6 of 12 reviewed concepts in this operating modelOpen operating-model research →

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