The number of flights and passengers is constantly rising each year and the airports are soonreaching their capacity limits and have only limited possibilities to expand. This makes opti-mization of operational processes at the airport essential in order to maintain growth and thelevel of service for the passengers in the air transport system.Operations research aims to optimize efficiency in operational processes and three basic prob-lems, the gate allocation, the resource allocation and delay propagation problem are tailoredto the aviation industry and explained in this paper. Mixed Integer Programming (MIP)Modelling and data from a European airline and a European airport is used and significantimprovements are achieved