Michael Kuziw comments

A few things to clarify here.

No where in the article does it suggest these will be regularly scheduled flights, however it does allow the airport to offer up those slot times should they be viable to the airlines.

This may be an ideal time for cargo flights to arrive, so perhaps consider spending less in 2019.

Also, there have been several issues recently regarding the cancellation of flights if they know the flight cannot arrive within the allotted runway usage times. With the hour extension, flights that are delayed still have the option of at least carrying their passengers to their destinations.

Also, Narita is a huge hub which means it is not the final destination for many. I'm sure they would consider offering later slot times to majority transiting flights instead of forcing passengers to disembark to an empty airport with no means of transportation.

Give them some credit guys.