// Use when advertised flight price seems too good, or when comparing LCC vs legacy carrier total costs. Triggers on hidden fees, baggage cost, true price, real cost, checkout surprise.
Use when planning flights, comparing ticket prices, or asking about flight costs, airline fees, travel dates, or route options. Triggers on booking flights, cheap tickets, flight search, vé máy bay, săn vé rẻ, tối ưu chi phí bay, đặt vé, virtual interlining, or any flight-related cost question.
Use when traveler has flexible dates and wants to find the cheapest departure/return combination. Triggers on cheapest day to fly, flexible dates, when to book, price calendar.
Use when looking for airline promo codes, flash sales, or credit card discounts before booking. Triggers on promo code, discount, sale, deal, coupon, cashback, loyalty discount.
Use when deciding between flexible and non-refundable tickets, or when travel plans might change. Triggers on refundable vs non-refundable, cancel risk, change fee, should I buy flexible ticket.
Use when searching for flights, comparing airlines, or finding virtual interlining combinations across multiple carriers. Triggers on find flights, search routes, compare airlines, best price.
Use when user explicitly asks about hidden city ticketing, skiplagging, or throwaway ticketing. Requires explicit consent before analysis. Triggers on hidden city, skiplag, get off at layover.
| name | fee-analysis |
| description | Use when advertised flight price seems too good, or when comparing LCC vs legacy carrier total costs. Triggers on hidden fees, baggage cost, true price, real cost, checkout surprise. |
Airlines - especially LCCs - intentionally show low base fares then add fees at checkout. This skill strips away the deception, calculates what you'll actually pay, and re-ranks options by true cost. A $89 Spirit ticket that becomes $275 after fees loses to a $189 Southwest that includes everything.
flight_options[] from flight-search skillbaggage from traveler profile (carry_on | checked_1 | checked_2)loyalty_programs[] from traveler profilepreferred_payment (credit card type, if known)Read references/airline-fee-matrix.md for comprehensive fee data by airline.
For each flight option, compute:
true_total = base_fare
+ taxes_and_surcharges
+ carry_on_fee (if LCC and carry_on not included)
+ checked_bag_fee (× number of bags × number of passengers)
+ seat_selection_fee (if desired, per passenger)
+ meal_fee (if not included, long-haul)
+ change_fee_risk (weighted by probability from flexibility-analysis)
+ payment_surcharge (credit card fee if applicable)
Present each option with full fee breakdown:
Fee Breakdown: HAN → SFO, 2 Adults + 1 Child
Option A (VietJet) Option B (VN Airlines) Option C (Korean Air)
Base Fare $380 × 3 = $1,140 $620 × 3 = $1,860 $580 × 3 = $1,740
Tax & Surcharge $95 × 3 = $285 $120 × 3 = $360 $110 × 3 = $330
Carry-on (7kg) Included Included Included
Checked Bag (23kg) $45 × 3 = $135 Included Included
Seat Selection $12 × 3 = $36 Free $15 × 3 = $45
Meal Not included Included Included
Payment Fee $0 (debit) $0 $0
─────────────────────────────────────────────────────────────────────────
TRUE TOTAL $1,596 $2,220 $2,115
Per Person $532 $740 $705
Rank Change Was #1 → Still #1 Was #3 → Now #3 Was #2 → Now #2
Critical insight: When true_total changes the ranking from advertised price:
⚠️ RANK REVERSAL DETECTED:
Option X was ranked #3 by advertised price ($89)
After fees, it's actually #5 ($275)
Option Y was ranked #5 by advertised price ($189)
After fees, it's actually #2 ($189) - no hidden fees!
For each applicable fee, provide actionable avoidance advice:
Carry-on Fee (LCC):
Checked Bag Fee:
Seat Selection Fee:
Change/Cancel Fee:
Payment Surcharge:
Include for options with strict carry-on policies:
| Airline | Personal Item | Cabin Bag | Weight Limit |
|---|---|---|---|
| VietJet | 36×23×56cm | 7kg total | 7kg |
| AirAsia | 40×30×10cm | 54×38×23cm (paid) | 7kg |
| Spirit | 45×35×20cm | 56×46×25cm (paid) | None stated |
| Ryanair | 40×20×25cm | 55×40×20cm (paid) | 10kg |
| Southwest | No limit | 61×41×28cm | None stated |
| Vietnam Airlines | 56×36×23cm | 12kg (economy) | 12kg |
ORIGINAL RANKING (by advertised price):
1. VietJet $380 2. Korean $580 3. VN Airlines $620
TRUE RANKING (all fees included):
1. VietJet $532 2. Korean $705 3. VN Airlines $740
VERDICT: VietJet remains cheapest even after fees (+$152 in extras).
However, VN Airlines includes lounge access with Business Saver
that isn't captured in this analysis.