Should I replace T1 figher with T2 fighter in late game?

We first take a look at tanks and bot.

T1 and T2 tanks are different.
T2 tanks have problem to counter the dox and boom bot, so T1 tanks are still necessary in late game.
And of course, player can also use slammer or Dox to replace the T1 tanks.

T1 and T2 bots are different.
The T2 slammer are better than Dox to clear the T1 units.
But T1 bots can attract the high damage bullet from leveler, sniper, bluehawk, catapult.
So T1 bots are still useful in late game.

I just want to ask this question.
Should I replace T1 fighter with T2 fighter in late game?
Is there any advantage to keep producing T1 fighters?
Or I should build pure T2 fighters instead of T1 fighters?

T2 fighters are interplanetary units so that's one major reason you may wish to build them for. However I think a lot of players just try and amass a large fleet of t1 fighters (safety in numbers?) rather than smaller squadrons of T2 fighters.

T2 fighters good for air support your invasion on another planet. Also you can kill tons of air fabbers which players use on "own planets". Also t2 fighters with micro can outrange Zeus...
But if you need to get air advantage keep t1 fighters spam,cuz they works good vs any air.

I know the T2 fighter has special ability to fly to other planets.
But I want to focus on the AA ability.
For example, in a single large planet FFA.
When the game enters late game stage, T2 fighters can provide better cost efficiency than T1 fighters provide?
I don't know the real answer.
There are four possible answer options.
A) T1 is more cheaper, and we don't really need to build the T2 fighter.
B) T2 is more stronger, and we should retire the T1 fighters.
C) T1 and T2 fighters should be mixed for best cost efficiency.
D) It depends on your opponent.

http://pa-db.com/compare?u1=fighter&u2=fighter_adv
T2 fighters take 3.7 times of metal than T1,
but they get double hp, three times rate of fire, 20% longer weapon range, and 5.625 time DPS.
Thus, I guess the answer is B.
I don't know in what situation I should use T1 fighter for better quantity with the same metal.
T2 fighter seems to be better in almost every aspect except the T2 factory is much more expensive than T1 factory.

I'd say C- resources are usually not much of an issue in late game, however build space and time are. As a result, keeping your t1 factories going with t1 fighters *and also* building t2 fighters with your t2 factories will result in more air power than just the t2 factories. I guess if you need metal for a specific project (titans or nukes or something) then turning the t1 facs off would make sense (once you have sufficient t2 air factories to maintain air control).

My usual approach to PA though is more factories working is always better (apart from a few specific scenarios, e.g. your opponent is dug in on a gas giant with no land or air).

I think that the resource are always an issue in late game.
Player can spam the advance factories to increase the consumption speed of metal.
It is true especially in a single large planet FFA since there is no planetary weapon to use.
And players will make Zeus with air fighters which can support it.

I usually still produce the T1 fighters in late game because the T1 air factories are still there to be used.
My question is more like that I should spam T2 or T1 air factories in late game when I need more air fighters.

Make some try with your different option.

For the same cost of metal only T1 and only T2: do the fight T1 vs T2 and you will see how many of witch one will left at the end.

Make for all of your option and you have your answer.

@huangth - do a single player game with cheat/dev mode enabled, spawn x amount of t1 fighters and x amount of t2 fighters, and smoosh them together. Experiment with formations and micro. See what happens

Do the science!

Phoenixes are very good at killing t1 fighters, however, t1 fighters are still a ******* awesome t1 unit. In theory they should outclass them, but they really don't until the very late game. Getting phoenixes is way too expensive and slow most of the time, and you can easily lose the air game if you try to rush t2.

However, phoenixes are much, much tankier than t1 air, they're also bigger and stack less, making them much better at surviving flak, Zeus and colonel AoE. If you're playing a big map with high amounts of metal, you should stop making t1 factories in late midgame and start pumping out phoenixes.

About the idle t1 factories, I found that t1 bombers + t1 fighers + phoenixes + kestrels is an awesome air deathball.

After some observations, here is my conclusion: T2 fighters are better than T1 fighters.
If you want more fighters and you can afford to spam T2 air factories, just do it!
Don't spam T1 air factories again unless you need the fighters immediately.

T2 fighters have superiority of weapon range, DPS, and HP.
With some micro, they can take out the T1 fighters without suffering too many loss.

I agree, the only downside I can think of is that the hummingbird is slightly faster than the phoenix.

to answer the OP:
no

t1 fighter is always better. interplanetary flight is a niche thing you only do when they are turtling another planet with bombers

It is a good tactic against some players.
Usually when players see that they are alone they switch to air builders (lots of them).
When you send a squad of 10 t2 fighters and fly over their entire planet you have a good chance of destroying all their air fabbers...

What would make the phoenix viable/useful?

Competitive players almost never go t2 air. One single t2 fighter can in theory destory any number of t1 fighters though. T2 air is **** though. The pathing is godawful prevting all of the anti ground units from fulfilling their roles. Air dominance between good players now is just spam hummingbirds and build more air factories... Maybe sneak in some bombers.
Air is too squishy, too efficiently countered, and t2 is too stupid to use.
I know many players think air snowballs too hard or is too fast or this or that, but it takes a skilled player to get anything useful done with their air.
The game though is pretty well balanced, but in free for alls, i never build air until i want zeus. Theres not much good ways to micro air so you will always get roughly equal trades on fighters. T2 flak one shots t1 for no good reason. Two shot i could understand. Air has problems.

I don't know your rank in 1vs1, but I think your play style is unable to against high rank players.
In my opinion, you should never forget the air units
unless you are in close combat with your opponent who lands next to you.

Without air units, you may encounter may problems.
You are unable to fly by the enemy base and gather more intelligence.
Radar can only know where the enemy are going, and you may know the content of the troops too late.
And you may expand slower than your opponent if he/she use air fabricator to build the metal extractors.
Air fabricators are risky to use, but if you don't scout them frequently, just few fabs can expand metal very quickly.
With air fighters and bombers, you can catch enemy fabricates which is without protecting.

And the fighters are still can be micro.
Try to make your fighters ball smaller and compact, and only fly by the border of enemy air groups.
You can destroy more fighters while suffer less loss.
And T2 fighters do even better job than T1 fighters for this.

I also think T2 flak should one shoot T1 bombers.
If you have seen bomber sniping commander, you will know why.

im a top ten player and almost never lose in ffas. i think i know what i am talking about.
You don't need air to get information, and you don't need air superiority to get information with air. You can accurately guess army compositions easily by size, time of game, and density. If you have to scout at the last moment to know what is coming at you, you are doing something wrong anyway.
alos note i didn't say "forget air units," I was speaking about free for all situations.
also it doesnt matter if you expand slower than your opponent when you are negating an oppoents factories at a fraction on the cost.

I don't know I've always had a better time using t2 fighters. They just seem to win more. They also kill zeuses easily. T1 fighters just fall out of the sky.