At approximately 2:20 pm Arizona time on 2/21/2018 I witnessed the following UFO Sighting event. Two fighter jets that appeared to be F-15's flying at about 10 k-15 k feet approached Lake Havasu City from due west. I am not a military jet expert and can not definitively identify their models. Both jets left double-wide contrails. Although they both left contrails, there were maybe a dozen instances where they stopped leaving contrails for a few seconds, or left contrails in "Morse Code"-like patterns before steady contrails resumed. Both jets had swept wings. They made some very unusual sharp turns which caused me to notice and observe them. They zig-zag in unison over a wide swath over the area for about 10 minutes, then flew back in the direction from which they came. There was something up there with them. It was a long white UFO. Compared to the jets, it was maybe 3 to 4 times as long and from my vantage point seemed to be about as wide as the fuselage. It did not leave a contrail. The jets appeared to chasing it. I only saw the white UFO briefly. I did not notice it until well into the event at which point it was about 60 degrees above the horizon north east of my vantage point. I watched it for about 15-20 seconds then knocked on our front door to get the wife to come out and see it. When I looked back in the sky I had lost track of it. The jets continued to zig-zag across the sky for maybe 5 more minutes before flying in a straight line back in the direction from which they came. 
While the jets were making their departure I talked to one of my neighbors who also observed the UFO Sighting event, but she did not see the white UFO. mufon cms# 90354