SEATTLE - A sign of the worry came in the form of a tweet linking to the on-line aviation blog L.A. Airspace: "United removes last 747 flight from Los Angeles."
While just a piece of a broader picture, the story captures the anxiety some feel about the future of the venerable Jumbo jet, as fewer airlines fly it in favor of smaller Boeing 777s or larger Airbus 380s.
In response United Airlines spokeswoman Mary Ryan said, "We have not announced any plans to retire our 747s. The up and down gauging is just a matter of optimizing our fleet by using the right aircraft for the right routes."
While United is moving away from the 747-400 between LAX and Sydney, Australia, it's adding more 747 service at its main hub in Chicago, replacing some 777s there with 747-400s. United operates 23 Jumbo jets.
Leeham & Co. airline analyst Scott Hamilton expects United to eventually replace its 747-400 fleet with other Airbus and Boeing jets.
"If United were to also become a 777X customer, you know that's going to replace the 747-400," Hamilton said.
The new 777X-9 is expected to hold 400 seats, about 10 to 15 percent fewer seats that the new 747-8 Intercontinental with a typical seating configuration of 460.
The business of flying has changed a lot since the 747's introduction in 1970, when Jumbos flew major trunk routes between big cities such as New York to London.
Over four decades the world has seen a shift to more direct routes connecting smaller cities like Seattle and larger markets with increasing frequencies This has lead to strong orders for smaller two-engine airliners with longer ranges including the new Boeing 787 Dreamliner and the new Airbus 350.
Boeing isn't ready to put the 747 out to pasture because there's nothing else like it, especially as a freighter. The new 747-8 comes as a freighter and a passenger version called the Intercontinental.
But so far only Lufthansa, Korean and Air China have ordered the passenger version of the plane. Two-thirds of the orders are for freighters where the 747-F faces little direct competition. The Airbus 380 doesn't come in a freighter configuration.
Boeing says it's still in direct talks with interested airlines for the new 747-8 in both freighter and passenger configurations, and believes the next 20 years will see sales of more than 700 very large airplanes by all manufacturers.
But so far in 2013, Boeing has seen a net gain of zero new sales with an order for five new jets offset by cancellations of five others.