What is pilot bidding?
Each month, Part 121 airlines publish a 'bid package' — the set of available pilot schedules ('lines') for the next bid month. Each line is a 30-day schedule with specific flights, days off, layovers. Pilots bid on lines by seniority; the most senior pilot gets their top choice, then the next, and so on.
Why bid lines monthly? Because routes + crew assignments change frequently — new equipment, retirements, base changes, seasonal demand. The monthly bid is the rhythm of Part 121 ops.
LINE bidding: rank lines by preference
LINE bidding is the older model. Each pilot lists every available line in their preferred order. The awards algorithm processes pilots in seniority order: most senior pilot gets their #1 line, second-most-senior gets their highest-ranked still-available line, and so on.
Strengths: simple to understand. Pilots see exactly what they're going to fly. Easy to predict.
Weaknesses: pilots must rank every line. With 200 lines, that's a lot of ranking. If your preferences don't match what's available, you might end up far down your list.
PBS: bid rules, not lines
Preferential Bidding System is the newer model — pilots bid rules instead of lines. Rules like 'I want 12+ days off', 'I avoid LAS layovers', 'I prefer weekend trips', 'no redeyes'.
The awards algorithm processes pilots in seniority order: for each pilot, the algorithm filters available lines by their hard rules, scores the remaining lines by soft-rule weights, picks the highest-scoring line, lowest line-number tiebreaks.
Strengths: pilots don't have to rank 200 lines. The system finds the best fit automatically. Operators can adjust the rule catalog without reprogramming.
Weaknesses: harder to understand 'why did I get this line?'. Rule conflicts are common. Tuning the rule catalog takes iteration.
When carriers pick each model
LINE bidding fits regional carriers + low-cost carriers with stable schedules + smaller pilot rosters (< 500 pilots). Pilots can reasonably rank every line.
PBS fits mainline + major carriers (1,000+ pilots) where ranking every line is impractical. Most of the major US legacies (Delta, United, American, Southwest) and many low-cost carriers (jetBlue, Spirit, Frontier) are now PBS-only or PBS-primary.
Some carriers run both — for example, a carrier might offer LINE bidding for senior pilots (who get the lines they want) and PBS for junior pilots (where the rule-based fit is more important than picking specific lines).
How AviationAlley handles both
AviationAlley's bidding module supports both LINE + PBS. Each bid package has a mode field — LINE or PBS — and the awards algorithm branches on that.
The PBS rule catalog ships with 8 rule types: DAYS_OFF, DAYS_OFF_COUNT, CREDIT_RANGE, MAX_LEGS_PER_DAY, AVOID_LAYOVER_CITY, PREFER_LAYOVER_CITY, AVOID_REDEYE, WEEKEND_OFF. Each has a hard/soft flag + weight. Operators with union-specific rules (FedEx, Delta, ALPA contracts) add custom rules via paid scoping.
The awards algorithm is a pure function: same input always produces the same output. Re-running awards is safe. 11 unit tests cover seniority ordering, hard-rule violations, soft-rule scoring, fallback when no line satisfies all hard rules, reserve fallback for unawardable pilots, tiebreaker, and determinism.
Frequently asked questions
Does AviationAlley support FedEx-style seniority logic?
The base awards algorithm processes pilots in seniorityNumber ascending order. FedEx-specific logic (separate captain / first officer pools, junior-available-list cascades) is paid scoping on top of the base. Same for SWAPA's PBS contract — base PBS is in; SWAPA-specific rules go on top.
What if no line satisfies all my PBS hard rules?
Fallback: the algorithm picks the line with the fewest hard-rule violations. You're informed which rules had to be broken. Worst case, the reserve pool catches anyone without an awardable line — typical at major carriers, 5-15% of pilots on reserve in any given month.
Can I run LINE bidding for some pilots and PBS for others?
Yes — bid package has a mode field, and you can publish separate packages with different modes for different pilot groups (e.g., senior pilots on LINE, junior on PBS). The awards algorithm runs each package independently.
How does the awards re-run work?
Awards is a pure function — same input produces same output. You can re-run awards as many times as you want; the platform replaces the prior award set with the recomputed one. Useful for last-minute schedule changes.
What's the reserve pool?
Pilots whose bid couldn't be awarded a line go to reserve. They're scheduled for ~3 days/month of on-call standby (round-robin across the month). Dispatcher callouts trigger when a flight needs coverage. Reserve days count toward FAR 117 caps.
Related guides
FAR Part 117 explained: pilot duty + rest rules for Part 121 air carriers
FAR 117 is the rule that caps how much a Part 121 pilot can fly in 24-hour, 7-day, 28-day, and annual windows. This is the practical guide for chief pilots, schedulers, and crew planners.
How to set up a 14 CFR Part 135 charter operation
Part 135 is the FAA certificate for on-demand charter and commuter operations. This guide covers the FAA's 5-phase certification process, Operations Specifications (OpSpec) authoring, AAIP setup, drug + alcohol testing program, and Avinode marketplace integration.