#explainer

7 articles tagged #explainer.

A row of ten slot tiles with eight lit and two dark beneath a large 80/20, on an Active Flights blog card.

Aviation27 Oct 20267 min read

Use It or Lose It: The 80/20 Airport Slot Rule, Explained

The 80/20 slot rule: fly a slot series 80% of the time or lose it. Where it applies, what COVID changed, ghost flights, and where the rule stands now.

A map of city dots joined by faint dashed candidate routes, with one route drawn bright and an aircraft on it, on an Active Flights blog card.

Aviation27 Oct 20266 min read

How Airlines Decide Which Routes to Fly

How airlines decide which routes to fly: demand, rivals, the right aircraft, airport slots, hub connections, seasons, and whether the route makes money.

Flight XX 123 drawn twice: variation 01 as two legs through a middle station, variation 02 as one non-stop leg, on an Active Flights blog card.

SSIM & Schedules27 Oct 20267 min read

Itinerary variation and leg sequence in SSIM

How SSIM names a flight leg: airline, flight number, itinerary variation and leg sequence. How variations are numbered, the overflow byte, and multi-leg dates.

Four one-letter service type codes — J, C, F and P — each with its meaning, on an Active Flights blog card.

SSIM & Schedules27 Oct 20264 min read

SSIM service type codes: what J, C, F and P mean

The one-letter service type on every SSIM flight leg says what kind of flight it is. What the codes mean, how to group them, and the traps when filtering.

A grid of aircraft seats with most of them lit up and 85.1% set large beside it, on an Active Flights blog card.

Aviation27 Oct 20266 min read

What Is Airline Load Factor? Why Planes Are So Full Now

Airline load factor is the share of seats an airline fills. How it's calculated, why it hit a record 83.6% in 2025, and what a full plane doesn't tell you.

A stack of five labelled SSIM record-type rows — a header, a carrier record, a flight leg, a segment record, and a trailer, on an Active Flights blog card.

SSIM & Schedules3 Dec 20254 min read

SSIM Chapter 7 record types, explained: reading a schedule file end to end

A field-level walk through the SSIM record types — header, carrier, flight leg, segment data, and trailer — with a sample file, the fields that matter, and the gotchas that bite parsers.

A raw fixed-width SSIM record line decoding into labelled structured fields, on an Active Flights blog card.

SSIM & Schedules12 Nov 20254 min read

What is IATA SSIM? A plain-English guide to the format that runs airline schedules

SSIM is how the airline industry exchanges its schedules — a fixed-width, 200-byte text format that's deceptively simple and genuinely hard to get right. Here's what it is and why it matters.