 By May 2018, there were over 30 projects, and short-haul hybrid-electric airliners are envisioned by 2032.The most advanced are the Zunum Aero 10-seater, the Airbus E-Fan X demonstrator, the VoltAero Cassio, the UTC modified Bombardier Dash 8, and the Ampaire Electric EEL.HEVs can be initially more expensive (the so-called "hybrid premium") than pure fossil-fuel-based ICE vehicles, due to extra batteries, more electronics and in some cases other design considerations (although battery renting can be used to reach the cost parity).