Talk about shock and awe. The massive orders placed by Persian Gulf-based carriers at last month's Dubai Airshow represent record numbers, both in terms of value and airline expansion plans. More than 400 orders were placed, including 225 for Boeing 777Xs for Emirates, Etihad Airways and Qatar Airways, launching the program. The Airbus A380 line was bolstered—or perhaps rescued—by a 50-unit Emirates order. But while large orders are always welcome news for the jetliner industry, it's time to consider the implications of these vast expansion plans.

First, look at Middle East orders as a percent of the total large jetliner backlog. While the region accounts for 19% of all outstanding orders for jets above 120 seats by value (using estimated discount prices), it accounts for about one-third of the twin-aisle jet orders (see graphic). That gives us an idea of these carriers' aspirations for international traffic moving forward.

All of these orders are not predicated on organic growth. The overwhelming majority of traffic carried by these airlines is not origin-and-destination (O&D); it is traffic between two other points transiting through a hub (Dubai for Emirates, Abu Dhabi for Etihad or Doha for Qatar). Dubai, which is far more of a tourism and business destination than the other two, still sees about 75% of its traffic transitioning to second international flights.

These carriers are blessed by great geography. In a time of expensive fuel, carrying jets with full tanks over very long ranges is simply less efficient than stopping at a hub that is conveniently positioned between Europe and Asia, India and Australia. They have also wisely focused on a high level of service for premium passengers, thereby reinvigorating competition in the international air travel market. All have received help from their home countries, but none of this support is nearly as important as the fundamentals of their business.

There is not much that the legacy airlines can do about the Big Three Gulf carriers drawing away traffic. European airlines have restructured into three large players and are belatedly trying to improve their products. Qantas Airways has simply decided to join rather than compete, signing a code-sharing agreement with Emirates. U.S. airlines, while less threatened due to different business models and much less geographic overlap, still face the prospect of Fifth Freedom flights impacting their transatlantic traffic.

These Gulf carriers face risks of their own. Landing rights need to be negotiated on a case-by-case basis, and market liberalization is not guaranteed. Infrastructure is not a problem, but congested airspace might be. An act of war or terror in the region could scare passengers away from the hubs, even for transit. The new long-range jets—the Boeing 787 and 777X and Airbus A350—could make long-range point-to-point flights more efficient, diminishing the economic appeal of hub-and-spoke operations. Financing all these jets may be an issue for Emirates, although Dubai's remarkable recovery from its 2008 financial meltdown is encouraging.

The biggest risk may simply be pushing the Gulf carrier concept too far. Much of the debate has focused on Emirates, which has done a remarkable job of growing at 15-20% per year for some time and as of 2012, it was the world's third-largest airline by capacity. Yet the two other Gulf majors have nearly identical business plans and equal or faster growth trajectories. Qatar's traffic has more than quadrupled within a decade. Etihad's grew by 23% in 2012 alone.

Compared with Emirates, the other two major Gulf airlines have much less experience, much less brand identification. Worst of all from the competing legacy carrier perspective, they have negligible O&D traffic, which means virtually all of their growth comes at the expense of other airlines. Also, unlike Emirates, their states have unlimited indigenous financial resources. They have a greater ability to spend heavily on expansion without much attention to making money. As Etihad and Qatar ramp-up capacity, there could be a negative impact on fares and industry profit.

The Dubai Airshow orders represent cash and program endorsements. But Airbus and Boeing need to be careful about how they regard these orders. Rather than being additive, they represent a different way of slicing the same pie. This means that jetliner orderbooks run the risk of fratricide. Basically, if these jets are delivered as planned, the legacy airlines will take fewer aircraft, and at a slower pace. OEMs need to be careful not to double count.

Contributing columnist Richard Aboulafia is vice president of analysis at Teal Group. He is based in Washington.