Air travel within living memory was expensive, formal and rare, and the transformation into mass transport followed identifiable policy and business changes.
The regulated era
Routes, fares and market entry were controlled by government in most countries.
Which meant airlines could not compete on price, and competition occurred on service instead.
The elaborate service associated with early air travel was a consequence of price regulation rather than of generosity.
Fares were high, load factors were low, and flying was the preserve of business travellers and the wealthy.
Deregulation
Removal of controls over fares and routes, beginning in one major market and spreading.
Which permitted price competition, new entrants and route restructuring.
Fares fell substantially in real terms over the following decades, and passenger numbers rose enormously.
Service levels fell correspondingly, which is the trade that price competition produced.
The hub and spoke model
Concentrating flights through hub airports rather than flying point to point.
Which allows more city pairs to be connected with fewer aircraft, since passengers connect rather than requiring direct service.
It also concentrates delays, since a disruption at a hub propagates through the network.
The low-cost model
A distinct operating approach rather than simply lower fares.
Single aircraft type, reducing maintenance and training cost.
Secondary airports with lower charges.
High aircraft utilisation through rapid turnarounds.
Point to point routing avoiding connection complexity.
Direct sales avoiding distribution costs.
And unbundling, charging separately for what had been included.
Unbundling
Separating the seat from baggage, seat selection, food and priority boarding.
Which allows a low headline fare with revenue recovered through ancillaries.
Ancillary revenue has become a substantial share of income across the industry, including at traditional carriers.
It also makes fare comparison genuinely difficult, which has attracted regulatory attention.
Aircraft technology
Fuel efficiency improved substantially across successive generations.
Which reduced the dominant operating cost and enabled longer routes with smaller aircraft.
Twin-engine aircraft cleared for extended overwater operation changed which routes were viable, replacing four-engine aircraft on long routes.
The environmental question
Aviation emissions have grown with traffic, and efficiency gains per passenger have been outpaced by volume growth.
Which makes it a difficult sector to decarbonise, given energy density requirements and long asset lifespans.
Sustainable fuels, efficiency improvements and demand measures are the levers under discussion, and none currently offers a complete answer.
Safety
Commercial aviation safety improved dramatically over decades and is now extraordinarily safe per distance travelled.
Which followed systematic investigation of every accident, mandatory reporting of incidents, and a culture of learning rather than blame.
The investigation model developed in aviation has been proposed for other sectors, including healthcare, with partial adoption.
Air traffic control
Coordinating aircraft in shared airspace requires substantial infrastructure and staffing.
Which is a constraint on capacity independent of runway or aircraft availability.
Airspace modernisation programmes have been under way for decades in several regions and have proven difficult to deliver.
Slots
Rights to use congested airports at specific times, allocated administratively and traded in some markets.
Which are extremely valuable at constrained airports, and the allocation rules affect competition substantially.
Use-it-or-lose-it rules requiring slots to be operated have produced flights operated with few passengers purely to retain the slot.
Consumer rights
Compensation regimes for delay and cancellation vary enormously between jurisdictions.
Which means the same disruption produces very different entitlements depending on the route and the carrier.
Claims can generally be made directly without paying a claims company a share.
Airports as businesses
Revenue comes from aeronautical charges and from retail, parking and property.
Which means non-aeronautical revenue is substantial and shapes terminal design toward routing passengers through retail.
Airport ownership models vary from public to private, with regulation of charges where market power exists.
Capacity constraints
Runway and airspace capacity limit growth at major airports.
Which produces long-running political disputes about expansion, weighing economic arguments against noise, air quality and emissions.
Those disputes have run for decades at several major airports without resolution.
Alternatives
High-speed rail competes effectively with air on routes below a certain journey time.
Which has produced substantial modal shift where the infrastructure exists, and several countries have restricted short domestic flights where rail alternatives are available.
The threshold at which rail wins is around three to four hours of journey time in the observed data.
Loyalty programmes
Now substantial businesses, with miles sold to banks for credit card programmes generating revenue independent of flying.
Which explains why award availability has deteriorated — the programme's revenue does not depend on redemptions being attractive.
Several airlines have been valued at less than their loyalty programmes during difficult periods.
Regional connectivity
Air services to smaller communities are frequently uneconomic and are subsidised in several countries as a public service.
Which is justified on connectivity grounds and is periodically reviewed against cost.
Withdrawal of services has substantial effects on remote communities.