The results of numerical calculations of the propagation of internal gravity waves (IGW) in a plane dissipative atmosphere with temperature and wind profiles are presented. The IGW are excited by a source at a height of 10 km in the troposphere. It is shown that a steady wave regime sets in within several tens of wave periods after the source in 'switched on. ' It is noted that when the jet stream is traveling at a moderate velocity in the stratosphere, it intensifies the IGW propagating counter to the jet (westward in winter and eastward in summer). When the jet stream is traveling at a high velocity a strong reflection of the oncoming IGW occurs; therefore the IGW propagating in the same direction as the stream dominate.