Air Traffic Control failed to inform the pilot of the reason for the 30-minute holding time during a ground stop.

Air to Ground Message: ATC SAID THEY JUST WENT BACK INTO GROUND STOP AN TO EXPECT ANOTHER 30 MIN HOLDING TIME BUT EWR DID NOT TELL HIM WHY.. NAS STATUS SAYS ITS FOR FLIGHT CHECK OPS.. Area: Philadelphia, PA, USA Type: Boeing 737 MAX 8 A: #a9546590dfd F: #fec0ee047ce #acars #vdlm2

Air to Ground Message: ATC SAID THEY JUST WENT BACK INTO GROUND STOP AND TO EXPECT ANOTHER 30 MIN HOLDING TIME BUT EWR DID NOT TELL HIM WHY.. NAS STATUS SAYS ITS FOR FLIGHT CHECK OPS. Area: Philadelphia, PA, USA A: #a9546590dfd F: #fec0ee047ce #acars #vdlm2