We measure the lasing dynamics of single and coupled photonic crystal nanocavity array lasers fabricated in the indium gallium arsenide phosphide material system. Under short optical excitation, single cavity lasers produce pulses as fast as 11 ps (full width at half maximum), while coupled cavity lasers show significantly longer lasing duration which is not explained by a simple rate equation model. A finite difference time domain simulation including carrier gain and diffusion suggests that asynchronous lasing across the nanocavity array extends the laser's pulse duration. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3116563]