It explain in full confidence about how contrails will form from a jet engine. While the explanation seems logical, notice that it is lack of quote. All the explanation comes from the writer own opinion.
Because of that, we have to consider all explanation in that website to be the opinion of one person only. He provide quote and link here and there but all of that do not directly answer the topic but only mention fact that can be used in any other way.
Scientist is not even sure how contrails happen. They can't even model it properly. Many are still trying to grasp of what happen. From time to time they notice anomaly which is surely will not be mentioned on the above website.
Article bellow mention anomaly of creation of contrail above critical temperature:
Measurement of the growth of the ice budget in a persisting contrail
The measured water mass within the contrail was found to be four orders of magnitude greater than that computed as a combustion product
Appleman was the first to develop criteria for contrail formation over a wide range of altitudes, temperatures and humidities. An essential result of his study was the prediction of wether water saturation is reached following the mixing of the exhaust heat and water vapor with the ambient air. His treatment describes the change in mixing ratio (decrease) in the aircraft wake as bein proportional to the change in wake temperature (decrease) with the proportionality constant fuel-dependent only. With any given fuel there results a critical temperature for each altitude above which contrail formation is impossible. In order that the contrail be visible a temperature as much as several degrees bellow the critical temperature is generally required.
In this experiment, as shown in Fig. 5, we actually observed the contrail to form and grow at a temperature several degrees above the critical temperature as defined by appleman, or the laboratory contrail studies of Pillie and Jiusto.
Article bellow mention anomaly of contrails that last for hours, many other article also mention contrails life of in situ sampling is under 30 minutes:
On the Transition of Contrails into Cirrus Clouds
Although several model studies concerning the formation and evolution of cirrus clouds and contrails have been performed (Starr and Cox 1985; Heymsﬁeld and
Sabin 1989; Sassen and Dodd 1989; Jensen et al. 1994; De Mott et al. 1994; Ka ¨rcher et al. 1996; Gierens 1996; Gierens and Jensen 1998), the detailed processes are far from being understood by now, mainly due to the few observational data available. New in situ and remote
Contrails older than a few minutes proved to be difﬁcult to sample in situ because such contrails, even if visible from far below or aloft, are in most of the cases difﬁcult to recognize and thus to follow while ﬂying on the same level. In most of the cases the optical contrast to the environment was very low. Following different jet aircraft during more than 60 occasions, contrails older than about 10–15 min could only be identiﬁed and sampled in very few cases. This raises the question whether very low concentrations of upper-tropospheric ice crystals frequently occur under conditions that are also favorable for contrails to form and persist.
Mention how contrails produce two kind of cirrus clouds:
In both cases two modes can be distinguished: one cloud mode around Dm
5 15–20 mm (Cf: 10 mm) and a second one toward submicron sizes to the left, which we call ‘‘haze mode.’’
Environmental conditions required for contrail formation and persistence
Contrails are frequently visible at distances as close as 25-35 m behind the aircraft engines. Using an analytical model of ice crystal growth in the exhaust plume, showed that the number density of ice crystals nucleated must be at least about 10^4cm^-3 in order for the contrail to be visible this quickly...... The simulations suggest that freshly nucleated sulfuric acid/water aerosols could not grow large enough to spontaneously freeze in the time required.
People who debunk chemtrail mention that scientist consider it as contrail. However some quote above show that even scientist are not sure of what they observe.