This paper proposes a solution to increase the probability of a wirelessly interconnected platoon of vehicles being string stable under packet loss conditions without imposing additional requirements on the communications system. The string stability of a cooperative adaptive cruise control (CACC) is known to be achievable if no communication errors occur. However, this is an assumption hard to achieve, in particular for wireless communications. The proposed system consists of a CACC controller that switches between the signal transmitted from the previous vehicle (when available) and the estimated signal from an observer. This paper shows that the inclusion of an observer can improve the performance of the quality of control when packet losses are considered.