SoftBank subsidiary HAPSMobile signed a partnership and invested in Alphabet’s Loon business, with the two set to work together on promoting the use of high altitude communications systems.

The deal covers a $125 million investment by HAPSMobile in Loon and includes a provision for a reciprocal investment at a later date.

In a statement, the two said they are actively exploring commercial collaborations to accelerate the deployment of high-altitude connectivity systems. The partners’ ultimate goals are to expand mobile internet penetration levels, enable IoT applications and assist deployment of 5G.

Topics being discussed include a bilateral wholesale deal; a common ground station which could be deployed globally; adapting Loon’s fleet management system for use by HAPSMobile; and creating an alliance to lobby regulators and officials.

President and CEO of HAPSMobile Junichi Miyakawa said “building a telecommunications network in the stratosphere” is a “major challenge” for parent SoftBank.

The collaboration with Loon will see the companies pool “technologies, insights and experience”, he added.

HAPSMobile’s technology centres on providing mobile coverage to remote areas and disaster sites from its Hawk30 aircraft. Loon has similar use cases, but delivers the signal from high-altitude balloons. It has already provided coverage in Puerto Rico in the wake of Hurricane Maria.