Chi Coms testing and probing to see how the US responds.  Do not like our tactic of putting out these surveillance planes without any kind of air escorts or backup.  Asking to have another
embarrassing incident  like what happened in 2001 when  their fighter plane collided with our plane and forced it to land on Hainan Island.
The Chi Coms  would not allow us to fly the plane out after the crew was released and the plane had to be dismantled and flown out
on a large air cargo transport plane. Even more humiliating in the years since,  US intelligence has determined that the Chi Coms had indeed been able to gleam important methods and
technology from the recon plane as the crew had not been able to properly destroy the spying equipment that was on the plane as they had not been properly trained for such an
eventuality and did not have the means to do so.  The Chi Coms love to make the US look like fools.  Do not want to see this happen again.