TFS (strings of letters)

Question

Complete the image below with the correct strings of letters in the correct squares (four squares will be left empty).

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Transcription (■ is a square that does not exist in the image, and ? is a blank square. Ignore the header row.):

MAKANAAS	■	HOISNAWA	ASKY	?
?	■	II	■	NENDTSANTAPIRINA
RE	DA	IA	■	KADAREEYCORKNATA
?	?	?	?	IOMAON
?	■	■	■	?
?	?	EEAS	NATA	ND

Answer 1

The completed image should look like this:

MAKANAAS	■	HOISNAWA	ASKY	*NA*
*IADOUT*	■	II	■	NENDTSANTAPIRINA
RE	DA	IA	■	KADAREEYCORKNATA
*■*	*■*	*■*	*■*	IOMAON
*ONIAINNG*	■	■	■	*IA*
*NTIA*	*AH*	EEAS	NATA	ND

But why? Well, each box here contains:

A string of the last two letters of US states beginning with the same letter. Where more than one state exists with the same starting letter, the two-letter-sequences are ordered alphabetically by the state's full name. For example, the first box 'MAKANAAS' represents the last letters of ALABAMA, ALASKA, ARIZONA and ARKANSAS.

We start in the top left corner with states beginning with 'A' and snake around the grid letter by letter, ignoring letters which do not begin any US states (like B and J...). Doing so means that our gaps can be filled thus:

R2C1: C - CalifornIA, ColoraDO, ConnecticUT = IADOUT;
R1C5: L - LouisiaNA = NA;
R5C5: P - PennsylvanIA = IA;
R6C2: U - UtAH = AH;
R6C1: V - VermoNT, VirginIA = NTIA;
R5C1: W - WashingtON, West VirginIA, WisconsIN, WyomiNG = ONIAINNG;
R4C1-4: All blank - we have reached the end of the alphabet!

As for the title:

'TFS' is the initial letters of 'The Fifty States'! This suggests we should be looking at letters which appear in the names of the 50 US states. The fact that each box contained an even number of letters set me thinking about pairs of letters, and the solution (eventually) followed...

There was also an extra, really quite large clue here, which I did not spot until after the solve when the OP commented below. The OP's choice of the unusual path shape is not arbitrary... If you turn the grid on its side, the shape of it is clearly a number '50' - had I spotted that I would in all likelihood have started thinking about US states much sooner - d'oh!

A fully detailed diagram can be seen here: