This paper addresses the impact of transportation delays on the performance of single-product continuous flow production lines of two machines separated by one buffer. Operation-dependent failure model (ODF) is considered for the machines, i.e. a machine cannot fail if it is not working on a part. Volume to failure and machine repair times are exponentially distributed random variables. We prove that the high the delays, the less the throughput of the transfer line. Numerical results show that this result holds under more general conditions.