Their expansion reflects the determination of the energy-rich Gulf states to develop new sources of income to reduce their dependence on oil, the price of which is plunging on world markets.
Government-owned Qatar Airways on December 22 takes delivery of the first A350 XWB (extra wide body) next-generation plane from European maker Airbus, designed to compete with US rival Boeing's long-haul fuel-efficient jetliners.
With orders for 80 of the planes, Qatar Airways is not only the launch customer but also the largest single customer of the A350 so far.
"Qatar Airways is a very ambitious airline. It has been not only undergoing rapid growth, but it has also focused intensely on its service offering," said Addison Schonland, a US-based aviation consultant with AirInsight.
Qatar Airways chief Akbar al-Baker has described the delivery of the A350 XWB as the "second significant fleet milestone" for the carrier after recently receiving three of 14 A380 superjumbo planes bought from Airbus.
The first commercial Qatar Airways A350 flight is scheduled for January 15 to Frankfurt, the hub of Lufthansa, one of the major opponents of the push by the Gulf carriers into Europe.
Qatar Airways is expanding on European routes, and has announced increases to the frequency of flights to Barcelona, Manchester, Stockholm and Copenhagen.
The airline is growing its fleet of 142 young planes at full throttle. At Britain's Farnborough Air Show in July, it also ordered 100 Boeing 777X aircraft.
It says it has total orders for more than 340 aircraft with a value of $70 billion.
In April, Qatar opened its long-delayed Hamad International Airport, which cost $15.5 billion and has an initial capacity of 30 million passengers a year.
Signup to our newsletter and follow us on Facebook and Twitter!
Qatar Airways, whose home country has a population of just 2.2 million, transported more than 18 million passengers last year.
- 'Gulf Three' threat -
"Having a deep pocket owner means the airline can ensure its fleet stays young," said Schonland.
This "makes it tough" for less nimble competitors with older planes and higher costs, he said.
The carriers dubbed the "Gulf Three", which also include Dubai's Emirates and Abu Dhabi's Etihad Airways, have transformed the region into a major hub for transcontinental travel, eating up a chunk of the so-called "legacy" carriers, many of which were formerly state-owned.
European airlines, notably Air France-KLM and Lufthansa, have voiced concern at increased activity by Gulf-based companies, complaining of differences in taxation that they say cause unfair competition.
Lufthansa voiced fears Europe would be relegated to "second league" in a September policy briefing, urging the European Union to apply competition rules to non-EU companies.
It complained that Dubai International Airport, which in 2005 had half the international passenger volume of Frankfurt airport, is now 50 percent larger than the German hub.
Qatar Airways chief Baker said at a recent aviation forum in Dubai that the legacy carriers complain because "they are inefficient".
But competition for Gulf carriers is also "getting tougher", especially from US legacy airlines, Schonland said.
"As we have seen in the US, legacy airlines tend to consolidate and then become hyper aggressive... I suspect the three Gulf carriers are going to see much more aggressive competition from the US legacies," he said.