A globally diversified conglomerate with interest in aerospace and building systems, United Technologies (NYSE: UTX) is one of my favorite low-risk investments right now. The F135 engine is the newest reason to hang your hat on UTX stock, and it will power the Lockheed Martin (NYSE: LMT) F-35 Lightning II fighter. That’s a great future revenue stream — but the long-term trends of United Technologies are what really matter to buy-and-hold investors. My relative-strength calculations show that United Technologies has performed 45% better than the S&P 500 over the past five years — with an average annualized return of 10% across that period. Since United Technologies builds jet engines, elevators and HVAC systems, it has a stable core business and isn’t going anywhere. Top it off with a hefty dividend history of payouts since 1936 — with a current yield of 2.6% — and you have a long-term investment you can believe in.