Airbus’s commercial aircraft chief, Christian Scherer, is quietly satisfied about the A320 family’s landmark achievement in overtaking the Boeing 737, its primary rival, in terms of deliveries.

“I don’t think about it,” Scherer admitted to FlightGlobal at the Dubai air show, stressing that he did not intend this to convey arrogance but rather his conviction that “it seems natural” that the “most capable” aircraft should be chosen to “escort the growth” of global air traffic.

Airbus chief executive Guillaume Faury remarked during the company’s recent third-quarter briefing that the A320, after 37 years, had “reached a major milestone, becoming the most-delivered airliner in history”.

“There’s a bit of pride here, as you can see,” he added.

The precise point at which Airbus nudged ahead will probably remain a subject of contention.

But its delivery figures for September this year indicated a total of 12,257 A320-family jets had been handed over by the end of the month – two more than the 12,255 claimed by Boeing for all variants of the 737.

Without detailed Boeing delivery dates, the crossover point is difficult to determine. But Airbus’s delivery of two A320neos, for SAS and Saudi Arabia’s Flyadeal, as well as a pair of A321neos, for Etihad Airways and Frontier Airlines, on 30 September confirmed it was ahead at the close of the month.

Its narrow lead of two airframes widened to 26 in October. Airbus delivered a further 64 A320neo-family aircraft during the month while Boeing achieved 40 for the 737.

Boeing handed over its first 737, to Germany’s Lufthansa, in December 1967 and was delivering the narrowbody jets for a little more than 20 years before Air France received the first A320 in March 1988.

But the different competitive and air travel environment – one in which Boeing still producing the popular 727 narrowbody trijet – meant this two-decade head start only equated to some 1,500 737s.

Over the years the two manufacturers each increased production. While Airbus has been gradually closing on Boeing, the delivery gap between the A320 and 737 was still more than 2,100 aircraft in 2010.

Airbus chipped away at Boeing’s lead by around 30-50 aircraft annually for much of the following decade, until the US airframer suffered a setback in 2019 when the 737 Max – in service for less than two years – was grounded over safety concerns in the aftermath of two fatal accidents.

Annual deliveries of 737s slumped from nearly 600 to fewer than 130 in 2019. The situation worsened the following year when Boeing suspended Max production for five months as the grounding dragged on, and the Covid-19 pandemic started causing global upheaval in the air transport sector.

The disruption tore into the 737’s lead over the A320 – halving it in the space of two years to 921 aircraft by the end of 2020 – and Airbus continued to hack away, substantially gaining on its rival even as supply-chain pressures dogged production ramp-up efforts during the post-pandemic recovery.

Boeing ran into further problems last year, facing intense US FAA scrutiny of its production quality following the in-flight separation of a 737 Max door plug.

The regulator capped monthly Max output at 38 aircraft – although this was academic, as Boeing rates were still lagging this figure considerably – and although Airbus had struggled to restore its pre-pandemic production level, it was still delivering sufficient A320neos to slash the 737’s lead to 60 airframes by the end of 2024.

That A320-family deliveries would overtake those of the 737 during 2025 seemed inevitable. But while the closure rate suggested Airbus might reach parity early in the year, bottlenecks in the engine supply-chain held up deliveries as the airframer was forced to stockpile ‘gliders’ – engine-less but otherwise completed aircraft – at its assembly facilities.

Airbus had parked around 60 A320neo-family jets by the end of June, when the delivery gap against the 737 was only 37 aircraft.

But an improvement in engine supply lines has since enabled Airbus to reduce the glider backlog, allowing the A320neo to catch up not only with its delivery schedule but also – at last – with its greatest competitor.