Flightpath is an xDS server that can configure Envoy to act as an Edge proxy for Consul Connect enabled services.
Flightpath registers itself in Consul Catalog as a Connect Native service and uses its own TLS certificate to configure routing in Envoy. Using these certificates Envoy can communicate with Connect Sidecars as if the connection was initiated by Flightpath.
Flightpath can be compared with Fabio or Traefik but it is not a proxy in itself. While both Fabio and Traefik manage cluster discovery and traffic routing themselves, Flightpath is only responsible for discovering the routing information from consul catalog and configuring Envoy to route the traffic.