Re: Dear AC
It's obviously arbitrary. If they had used a different measurement system (furlongs per fortnight?) they would have chosen a different speed target.
If you read it as "the team is attempting to push the car over the 1,609 km/h mark" it loses all sense. I do wonder why they chose to use English measures when this is obviously a global competition. Why not push for the 1500 km/h mark?
Actually, it makes most sense to first aim for the 1,235 km/h mark, the speed of sound. The added benefit is that you break the current record of 1,228 km/h which narrowly avoided breaking the speed of sound by only 7 km/h.