I would avoid the 737 if I were you, especially if you are flying in J. 788 J has lie flat beds, 737 J seats are comparable to the 788 PY seats. I rather fly ANY airbus than the 737. Actually, I rather fly 788 PY than J on a 737. Theres a whole thread on FT bout the new 737. Doesn't look like many people like the 737 J seats.
Is there any reason there's no J space available on a flight with a totally empty cabin? I've checked the seatmap and J is literally empty. The buckets are
J9 C9 D9 Z9 P9 R7 O9 E9 N7 Y9 B9 M9
U9 H9 Q9 V9 W9 G9 S9 T9 L9 A9 K0 if that helps anybody.
Are you booking on AP or actually buying the seats? FT talked about the AP booking website was down a couple days ago, then it was fixed, but could possibly be broken again. AC/AP and IT don't go well together
Keep in mind, just because there are J seats available for purchase doesn't mean AC will release those seats to AP. AP fixed mileage rewards only gets a VERY VERY LIMITED selection of flights and J seats. So even if that flight is released to AP for fixed mileage, there could only be 2 out of the 40 J seats available for AP fixed mileage rewards. Have you tried Market Rewards?