WASHINGTON — Inflight connectivity startup SmartSky Networks has pushed back the start date for its terrestrial air-to-ground network from late this year to mid-2018, the company said Aug. 3.

Charlotte, North Carolina-based SmartSky said 86 percent of the tower sites for its network of 250 ground stations across the United States have completed initial on-site viability testing, but are still in the process of finalizing permitting and backhaul-connections.

“Customers are unanimously impressed after experiencing inflight demos, confirming that we have significantly raised the bar for what will constitute best-in-class, future-ready airborne connectivity going forward,” SmartSky Chairman and CEO Haynes Griffin said in a prepared statement. “They seem equally appreciative of the fact that the few months of additional schedule to meet the high standards we have set for this network is ultimately to everyone’s benefit.”

Once complete, SmartSky will join Chicago-based inflight connectivity provider Gogo — a large buyer of satellite capacity — and London-based satellite operator Inmarsat in fielding ATG networks to connect aircraft in densely trafficked regions. Gogo has an ATG network across the United States. Inmarsat’s network, operated with partner Deutsche Telekom, spans Europe.

In contrast to Gogo and Inmarsat, SmartSky so far has not paired its network with satellite connectivity, though the company has expressed receptivity to working with satellite companies.

SmartSky said the remaining necessary ground infrastructure is being installed and commissioned upon completion of local permitting. Base station radio production and software optimizations related to FAA-granted supplemental-type certifications — regulatory licenses required for aircraft antenna installations — necessitated the additional time, the company said.

“SmartSky’s Early Bird customers and distribution partners have been notified, as consistent with the company’s commitment to timely updates,” SmartSky wrote.

SmartSky has raised around a quarter of a billion dollars for its ATG network, including a $170 million Series B financing round in March, and has network data centers in Ashburn, Virginia, and San Jose, California. The company originally anticipated having its network completed late this year.

Caleb Henry is a former SpaceNews staff writer covering satellites, telecom and launch. He previously worked for Via Satellite and NewSpace Global.He earned a bachelor’s degree in political science along with a minor in astronomy from...