In this forme, The Creator descends from the heavens to smite the evil and unjust with His extraordinarily powerful Judgment. Flying Arceus is not common due to two major downfalls. The first is a weakness to Stealth Rock; taking 25% each time Arceus switches in is not pleasant. However, Arceus doesn't take any damage from Spikes or get poisoned by Toxic Spikes, which makes Him an efficient stallbreaker. Secondly, Flying is a poor defensive typing, as the only useful traits it grants Arceus are a Fighting resistance and a Ground immunity. However, conversely, Arceus's STAB Flying-type attacks are only resisted by a few common Pokemon in this metagame, specifically Dialga, Zekrom, Tyranitar, and Jirachi. While other Flying-types, such as Ho-Oh and Shaymin-S, might seem to outclass Arceus in the role of an offensive Flying-type due to their abilities and better STAB combinations, Flying Arceus is the only Flying-type that can reliably boost His offenses to tremendous levels. Furthermore, Arceus possesses great overall bulk: after a Calm Mind or two, even super effective moves will fail to dent Him, and few Pokemon will be able to stand up against His wrath.
The main advantages of using Flying Arceus over other Arceus formes, or other Flying-types for that matter, are its excellent mono-attacking STAB and its ability to further boost its power. Many of the Steel-types in the tier, such as Ferrothorn, Forretress, and Scizor, have a secondary typing that makes them vulnerable to Judgment, allowing Arceus to capitalize on its Flying-type STAB quite effectively. Additionally, Arceus outspeeds the vast majority of the Uber tier and has great power and coverage with a single move, so it can easily wreak havoc if left unchallenged.
While Arceus's Flying typing gives it an unfortunate Stealth Rock weakness, this problem is somewhat mitigated by its incredible overall bulk and access to Recover. Arceus can augment its bulk further by using Refresh to prevent opponents from crippling it with status and stalling it out. However, if you prefer better offensive coverage to the ability to alleviate status, Earth Power is a viable option that can score a neutral hit on just about every Pokemon in the tier that resists Flying-type attacks. In fact, the few foes that resist the Flying / Ground combination, such as Skarmory and Thundurus, are outsped and 2HKOed by +1 Judgment.Team Options & Additional Comments >>>
Flying Arceus can also run a Swords Dance set somewhat effectively, using Fly and Earthquake for coverage, but this is largely outclassed by Normal Arceus, who packs STAB ExtremeSpeed. Furthermore, Fly's charge turn makes it much easier for opponents to switch in checks, such as Dialga and Skarmory, and neutralize Arceus's efforts. With Toxic Spikes support, however, Arceus can stall for more residual damage while it is up in the sky, causing the opponent to lose health much faster. Otherwise, shoehorning Flying Arceus into other roles simply highlights its poor defensive typing; if you're looking for a bulky supporter that deals with Groudon, Grass Arceus is far superior.
Checks and Counters
The mono-attacking set is wrecked by Zekrom, who can take even a +4 Judgment if necessary and OHKO Arceus with Bolt Strike or Fusion Bolt. Tyranitar can wall this set to infinity and beyond, but it can't do much in return if it lacks Stone Edge. A +6 Judgment can 2HKO specially defensive Tyranitar, however, so if you want to counter Flying Arceus successfully, Stone Edge is mandatory. Skarmory takes 58% maximum from a +2 Judgment, which allows it to use Toxic or phaze Flying Arceus out and then Roost off the damage. While Bronzong is not capable of phazing, it can set up Light Screen and Toxic Arceus while shrugging off hits with ease. Jirachi can shrug off most of Arceus's attacks as well, paralyze it, and proceed to whittle it down with Iron Head while recovering health with Wish. However, it has to be wary of Earth Power. Chansey and Blissey can also wall Arceus, but Arceus can set up on them if it has Refresh. However, +6 Judgment comes close to OHKOing physically defensive Blissey, and will 2HKO specially defensive Chansey, so it's only wise to use these as checks should Arceus lack Refresh, or should Blissey or Chansey be using Snatch or Calm Mind.
Choice Scarf Terrakion outspeeds Flying Arceus and has an 80% chance to OHKO with Stone Edge, Stealth Rock taken into account. Ho-Oh needs Stealth Rock off the field in order to reliably counter Flying Arceus, as the rainbow phoenix is 2HKOed by +1 Judgment, and can only OHKO with sun-boosted Sacred Fire if Stealth Rock is down. Choice Scarf Palkia can 2HKO Flying Arceus with a rain-boosted Surf and the aid of Stealth Rock, even if Arceus sets up a Calm Mind as Palkia uses Surf. Thundurus can take a +1 Judgment and OHKO back with a super effective Thunder, but again, only with Stealth Rock damage. Steel, Electric, and Rock Arceus also pose significant threats, taking little damage from Judgment, using Flying Arceus as setup bait, and threatening to KO with their own STAB Judgment.