Correct. What people don't understand is jet engine technology has significantly changed over time. As has fuel. The first jets created very significant trails because tolerances were poor and jet fuel was less refined. Air fuel mixtures were manually controlled based on temp readings and adjustments were based on panel scan times and differing weather as they traveled. In the 1970s, early computer controlled turbines entered the scene. Metallurgy, oil refinement, and engine tolerances all improved. This in turn changed engine temps and significantly changed exhaust characteristics. By the 1980s, this technology entered broad use and the nature of contrails began to change again. By the end of the 1990s, metallurgy and computer controlled turbine efficiency changed again. As did manufacturing technology of turbine blades, allowing for amazingly tight tolerances. As did anti-freeze fuel additives. This again changed exhaust profiles and contrails. I'm sure some level of research has taken place but it's certainly nowhere near as invasive as the conspiracy leads people to believe. For example, metal found everywhere. They claim it's in the fuel. This would be extremely abrasive and total turbine failure would be extremely common. Who would do this to multi million dollar turbines? Ignoring the fact turbines are more reliable than ever.