SAN DIEGO — As Airbus and Boeing raise production to all-new levels in response to record orders, both manufacturers say the global air transport industry is more resistant than before to market fluctuations and the potential threat of a ‘bubble’ which could drastically hurt the combined backlog of more than 10,000 aircraft.

Compared to the fragility of the backlog during earlier order-delivery cycles there are “a number of reasons to be reasonably optimistic,” says Airbus senior vice president leasing markets Andrew Shankland.

Speaking at the International Society of Transport Aircraft Trading (ISTAT) Americas 2014 conference here, Shankland notes global gross domestic product (GDP) has already grown to 3.2% in 2014 versus 2.3% in 2013—a year which saw Airbus take 1,619 net orders.

Revenue passenger kilometers and freight traffic have also shown early signs of climbing beyond 2013 levels and have to-date grown to 5.4% and 4.6% respectively in 2014. “It’s been very encouraging to see,” says Shankland.

Other factors, such as fuel costs and financing, which in past years have intensified the severity of boom and bust cycles, are also favorable, he adds. “There is plenty of financing available and fuel is relatively stable.”

Echoing many of these observations Boeing vice president marketing Randy Tinseth says the “market is looking a lot better today. We are being cautiously optimistic as we move forward. Today’s average load factor is 79.1% worldwide and we expect traffic growth to be around 6% for year.”

Like Airbus, Boeing also reports signs of a continued slow recovery in the cargo market which has been in the doldrums since 2011. “Over the last six to eight months we have seen progress,” he adds. “Airlines are also profitable, led by the U.S., and both the leasing and secondary markets are also faring well.”

Boeing finished last year with a record order backlog of around 5,100 airplanes valued at nearly $400 billion and expects to deliver as many as 725 aircraft in 2014. Airbus, which forecasts deliveries of 630 aircraft this year, has an even larger order backlog of almost 5,560. The backlogs represent more than eight years of work for both companies.

However Adam Pilarski, senior vice president of Avitas, cautions that “we are in a bubble environment,” and asks “are the existing orders and deliveries rational?”

While he believes the orderbook is sustainable if fuel prices stay high and new environmental rules are introduced, Pilarski says the overall importance of the fuel factor could reduce as oil becomes “less relevant in the future” to the global energy budget. “We have also seen a relatively weak recovery so far. Aircraft values are not doing well yet. We are just getting to the level where aircraft values are reaching base values,” he adds.

Pilarski also points to several potential vulnerabilities in the orderbook across various market sectors ranging from low-cost carriers in Asia (LCCs) to high reliance on groupings of carriers in specific regions. The three largest Middle East-based operators Emirates, Qatar and Etihad, for example, took 1.4% of the orders in 2000 and 5.3% in 2013, but will account for 8.9% of the orders in 2023.