Unmanned aircraft typically rely on radio frequency (RF) links for at least command and control (C2) and navigation, and may also employ RF links for other critical functions, such as position reporting through ADS-B or mode C transponders. Vehicles used in future On Demand Mobility (ODM) and Urban Air Mobility (UAM) operations, whether flown with no onboard operator or with a minimally trained onboard operator, are expected to be similarly dependent on RF links for navigation, control, and communication with Air Traffic Control (ATC) (whether by a human or an automated system). Loss of even one of these links can present a significant hazard. For example, recent UAS accidents have often involved lost communication links. As the level of autonomy of UAS increases, loss of C2 links may not be directly catastrophic though it is still likely to be disruptive to airspace operations, and other RF links, particularly satellite navigation links, become essential for maintaining safe vehicle operations. The challenges of maintaining RF links will grow as operations of highly autonomous vehicles expand, and as envisioned future concepts of operation become a reality. Future aviation systems such as UAS operating beyond visual line of sight (BVLOS) and air taxis operating as part of an envisioned UAM system will frequently operate at low altitudes far from established airports. At these low altitudes, terrain, buildings, and even vegetation can significantly impact RF coverage. This paper presents initial results of a research effort to integrate RF coverage analysis into the mission planning process for UAS and other future vehicles, such as air taxis. The overall research effort is developing tools to analyze coverage of both C2 and navigation links along an intended flight path, as well as automated path generation tools that produce mission plans that minimize the likelihood of RF link loss. This paper focuses on analysis of air-to-ground RF links, and mission planning to minimize the likelihood of loss of such links. Numerical examples focus on Manhattan, using a representative mission of passenger transport from LaGuardia airport to lower Manhattan to demonstrate both RF coverage analysis and path planning.