The United States and Cuba this week conducted a second round of talks on matters of civil aviation, but it remains unclear when regularly scheduled flights between the countries might finally be able to take off.

Officials from both nations, which recently reestablished full diplomatic relations after a hiatus of more than 50 years, had "a good, candid exchange of views" and were considering a third round of negotiations in the coming months, an unidentified U.S. State Department official told the Miami Herald.

One of the sticking points in the talks seems to be Cuba's desire for reciprocity, meaning Havana wants its state-owned airline Cubana de Aviación to be able to offer scheduled flights to the United States. U.S. carriers, meanwhile, are similarly "eager" to begin such services "as soon as possible," the official added.

Officials representing six U.S. government agencies and negotiators from Cuba's foreign ministry and the Cuban Institute of Civil Aviation all took part in the talks, according to Reuters.

Companies including American Airlines, United Airlines, Delta Airlines and JetBlue Airways, meanwhile, are all preparing resume scheduled flights between the countries, the Wall Street Journal reported. Scott Laurence, Jet Blue's senior vice president of airline planning, admitted, however, that it would be difficult to gauge demand given the market had been closed for decades.

"Operationally, we're absolutely ready to go," Laurence said. But "commercially, it's a little bit different," he cautioned.

Technical and regulatory challenges also remain and it is unlikely that regularly scheduled U.S.-Cuba flights would start before the end of the year, an unnamed State Department official told the Wall Street Journal.

Fights between the United States and Cuba already take place on a regular basis, but the connections are limited to charter services. Those circumstances will turn out to be an advantage, however, as safety and security cooperation are well advanced because of the existing operations, another unnamed U.S. official told Reuters.

For the most part, Cuban airports also already meet U.S. Federal Aviation Administration and Transportation Safety Administration standards, the source added.