Nowadays methods for solving the problem of estimating the temporal characteristics of data processing are well studied and based on the timing performed operations, the use of the network graph, the construction of the spanning tree, etc. However, in solving some problems of automating controls, there may be difficulties associated with modeling the information processing and obtaining adequate input data for calculating the indicator of the timeliness of the system function implementation. The article considers general issues of assessing the properties determining the quality of aircraft flight data, its feasibility and timeliness. A new approach associated with the model "the presence of exactly one error in the generated data volume" is proposed for assessing the feasibility of aircraft flight data. This model is applicable only in the case when the control of feasibility is carried out for the entire set of necessary data. For timeliness index assessment, it is proposed to present the structure of the automated data preparation system in the form of a sequence of technological sites. Having determined the execution time of functional tasks by elements of a typical site and probabilities of data distortion, it is possible to calculate similar indicators for each elementary process included in the data preparation process and the system as a whole. An elementary data preparation process, the essence of which is to update the system database is considered as an example. This stage is the most representative, since all elements of the technological site are involved in its implementation