Private carrier Bamboo Airways recently acquired slots to operate regular direct flights from Ho Chi Minh City to San Francisco and Los Angeles starting September 1.

The airline plans to begin charter flights starting July and regular flights in September with four flights a week.

The flights would be operated using the long-haul Boeing 787-9 Dreamliner aircraft. The carrier said it was rushing to complete the final steps in the process of building its personnel apparatus, including pilot and flight crew training, to get ready for operating direct flights to the U.S.

While the latest development stirs new hopes for direct flights between the two countries, something that airlines and officials have been discussing and working on for nearly two decades, there are still many hurdles to overcome.

Aviation expert Nguyen Thien Tong said that apart from flight slots, each Vietnamese airline will need to acquire various safety permits from U.S. agencies before getting the go ahead for direct flights.

Vietnam Airlines, with decades of experience in the industry, seems to be the most promising candidate to secure these permits, while Bamboo Airways, having operated for only two years, might face stiff challenges in proving its capability to conduct such long direct flights, he told VnExpress International.

Last September, national flag carrier Vietnam Airlines had became the first Vietnamese airline to secure permits from the U.S. Department of Transportation for direct flights to the U.S.

The airline last month received licenses from the Civil Aviation Authority of Vietnam (CAAV) to operate the Airbus A350 aircraft to the U.S. It had already acquired a permit for the Boeing 787.

Last year, Vietnam Airlines conducted over 20 charter flights between the two countries.

But, for regular flights, various permits are needed from the Federal Aviation Administration (FAA), the Transportation Security Administration (TSA) and the U.S. Customs and Border Protection (CBP).

The TSA is one of the toughest obstacles with its stringent requirements. It will send experts to examine Vietnamese airports before proceeding further.

A CAAV official told local media that the current fleet of Vietnam Airlines and Bamboo Airways with their Boeing 787-9 and the Airbus 350 won’t be able to fly directly to the U.S. at full capacity (over 300 seats).

For long direct flights, the Boeing 777x and Airbus A350-1000 are needed, but the two carries do not own such jets, he said.

Apart from concerns over technical challenges, experts have also questioned the profitability of Vietnam-U.S. direct flights.

Vietnam Airlines CEO Le Hong Ha said the carrier might have to bear a loss of $30-50 million a year in the first five years of operating direct Vietnam-U.S. flights.

Bamboo Airways chairman Trinh Van Quyet had earlier calculated that the airline could earn VND8 billion ($346,700) a month from direct flights with return ticket prices of around $1,300.

But it is difficult to confirm those figures, especially as U.S. airlines, such as United Airlines and Delta Air Lines have launched and suspended direct flights to Vietnam after making losses, Tong said.

There are currently no direct routes between the two countries, and passengers have to transit through Hong Kong, South Korea or Taiwan, taking 18-21 hours in all. A direct flight would shorten the travel time to 15-17 hours.

Tong also said that with the ongoing Covid-19 pandemic it is unclear when a regular direct route will be established.

Americans are among the top foreign visitors to Vietnam, with 687,226 arrivals in 2019, and an ethnic Vietnamese population of over 2.1 million in the U.S. is also expected to be a steady source of travel demand.