I was tracking this earlier and noticed it diverted to DTW enroute from AMS-IAH.
flightaware.com/live/flight/KLM6 … /EHAM/KDTW
Med perhaps?
There may be something in CADORS or the FAA Preliminary Accident & Incident Data on Monday or Tuesday.
It’s interesting that KLM doesn’t have a flight 61 in its system.
The AMS-IAH flights are 661 and 663. I’m wondering if 61 was a special flight for today. The flight only has operated, at least on the AMS-IAH route, a handful of times since September. Could it be that KLM uses single and double digit flights for extra sections much in the same way American carriers use 9000 series flights? (KLM does have 9000 series flights. These are operated by its partners.)
KLM661 was scheduled to depart AMS about the same time as KLM61. As of this writing about a dozen hours of the scheduled departure time for 661 the flight is still shown as “scheduled”. No indication of it taking off.
Delta is a KLM partner operating the AMS-DTW route. KLM may have routed the flight via DTW to take care of excess passengers and/or cargo from Delta or the stop could have been for operational reasons (e.g. stronger head winds than expected thus causing a need to stop for fuel).
Maybe they were bringing in an extra plane for snow delayed passengers?
KL661 is a codeshare flight with DL9386, KL663 is shared with DL9388.
The only oddity that I could find is that the aircraft used for KL663 is registered to PrivatAir (a subsidiary of KLM) and has registration number HB-JJA. (Pictures)
As far as ATC is concerned DL9386 doesn’t exist. The actual flight is KL663 so that’s what’s tracked.
Privatair is not a subsidiary of KLM.
It’s an independent company providing charters, corporate shuttles, and business class only flights for three airlines.
Lufthansa services
Frankfurt/Pune (India)
Muncih/Cairo
Frankfurt/Bahrain
Frankfurt/Dammam (Saudi Arabia)
Munich/Tel Aviv
Swiss International Air Lines service
Zurich/Newark
Air France/KLM service
Amsterdam/Houston
Their web site is privatair.com/
If you are referring to this:
then some definitions are in line:
subsidiary: a company that is completely controlled by another company
partner: a commercial entity with which another commercial entity has some form of alliance.
Privatair is not a subsidiary of KLM but rather is a partner.
Teamwork!!!
A friend of mine recently flew from JFK to Zurich on a Private Air BBJ and described it as the best airline, and service he has every experienced.
He also highly recommended Qatar Airlines, and one other I’ll have to get the name from him.
According to the Dutch newspaper De Telegraaf, the plane was diverted because of a medical situation:
A leukemia patient (described as a young girl) suffered from a stroke. Doctors couldn’t save her life and she passed away. To make the story even worse: The family was on their way to Houston to get treatment for her leukemia. 
BTW: Thanks Dami and Rob for the replies.
It’s usually an all-biz aircraft, the one used for IAH-AMS is a Boeing 737-700 BBJ.