Responded to the email (the contact form creates a new support ticket).
The a/c in question has its D check expired currently, as seen from the aircraft page: http://www.airwaysim.com/game/Aircraft/My/View/16451/
By default the system will perfom C/D checks to the planes whenever they expire. (Dashboard->Settings)
Looking at your system inbox, I see two automated D check messages, and in cash flow statement two ~9mil deductions for the checks. However it is not possible for the automation to start another check while the plane is already in maintenance (a very simple "0 or 1" trigger), so there must have been some other reason for it.
Looking at the game logs it appears that you have this morning made some manual maintenance actions to this particular aircraft, and I presume this is a cancellation of the ongoing D check which was started by the automation, am I correct? This is my assumption since the only way the system can do multiple D checks in a row is that first the maintenance automation (which is turned on by default) starts the D check (since it is going to expire - normal procedure), then you cancel it manually (for some reason; for example other plans for the aircraft) but leave the check still as expired (= no other manual maintenance actions) and keep the plane flying. Then the automation will again notice the expired check and send the plane again to the D check since one cannot fly with overdue maintenances (risk of heavy penalties for the company)..
The times seem to match my assumption since the automatic D check was started on 23-Feb-2000 game time and the manual maintenance action (check cancellation?) by you was made on 29-Feb-2000 (06.50 UTC this morning of May 20th) and the automation restarted the check on 01-Mar-2000 since it was expired and plane was flying on routes.
So looking at this data, the maintenance system works normally. But if you can clarify what maintenance actions did you do or intend to do with the plane this morning?
--(ticket created at 9:57am this morning and responded at 6:15pm)