Flight Rebooking Fee Calculator

Change requests arrive with fareClass, daysToDeparture, changeFrequency, and loyaltyTier at top level, plus passengerDetails and the original and new departure dates; those four scalar fields are what every fee table keys on.

Base fees form a matrix over fareClass and daysToDeparture, resolved with first hit: 'First' changes are free beyond 14 days and cost 50 inside it, 'Business' steps 75, 100, and 150 across the over-21, 7-21, and 7-or-fewer day bands, 'Economy' climbs 100, 150, 200, 250 as the window shrinks from over 30 days down to 3 or fewer, and an unmatched fare class defaults to 300.

Cheaper cabins paying higher and earlier-rising change fees is standard fare-fencing logic: flexibility is part of what a premium fare buys, so economy tickets carry the tightest restrictions. Fees stepping up as departure approaches track the airline's shrinking chance to resell the vacated seat; the specific bands and amounts are commercial policy, not regulation.

Repeat behavior scales the fee next: a changeFrequency of at most 1 keeps the frequencyMultiplier at 1 with 'No additional charge for first change', 2 to 3 changes raise it to 1.25, more than 3 raises it to 1.5 as a '50% surcharge for frequent changes', and a missing value defaults to 1.

Escalating surcharges for serial rebooking discourage treating changes as free options on seat inventory, a real cost since every change reopens revenue accounting and inventory control. The 25% and 50% steps are deterrence tuning rather than any industry standard.

Status pays off here: a loyaltyTier of 'Platinum' zeroes the fee through a loyaltyFactor of 0, 'Gold' halves it at 0.5, 'Silver' takes 25% off at 0.75, and everyone else keeps a factor of 1 with 'No loyalty discount applied'.

Concentrating full fee waivers at the top tier mirrors how change-fee forgiveness is marketed as an elite benefit in real frequent-flyer programs, since the fee revenue given up is small next to the retention value of high-yield flyers. The 50 and 25 percent ladder below it is plausible program design, not a rule.

One line settles the arithmetic: adjustedFee rounds modificationFee.baseFee * frequencyMultiplier * loyaltyFactor. Multiplying instead of adding keeps both the surcharge and the discount proportional to the base fee, so a Platinum factor of 0 wins regardless of change history.

Overrides get the last word through ordered conditions: loyaltyTier == 'Platinum' with daysToDeparture > 1 waives everything, an adjustedFee of 0 passes through as 'No fee applicable', same-day 'First' changes still pay a 100 minimum, any other change with daysToDeparture <= 1 pays max([200, adjustedFee]), and the default row carries adjustedFee forward as the 'Standard modification fee', in every case with modificationFee.allowed set true.

A same-day floor exists because last-minute changes hit operations hardest, leaving no time to resell the seat, so even heavily discounted fees are clamped upward. Exempting Platinum members from that floor only while more than a day out puts a deliberate limit on the waiver; the 200 and 100 floors are business amounts, not mandated fees.