Big problem with sun conure aggression

Hi, I'm new here, I had to register because I can't handle my parrot's behaviour anymore. Also, english is not my native language and I'm sorry for all my mistakes.
So, I have two conures, one is 3 years old, second about 1 year old. They're together a year, both of them are hand-feeded, but they like each other and get along very well. But older parrot is very aggressive. When I bought her she had clipped wings, when the feathers grew back I didn't clip them again, but it still caused that she is afraid of sitting on the floor. When she was young she attacked things like hands in cleaning gloves or plant sprayer and was very afraid of hoover, but I thought that it was caused by her cowardly charakter. But then she started to dislike more things and she started to atack my sister. I thought that it was caused by my dislike towards my sister. Also, she attacks every stranger or person who she sees rarely, but when she still was young (about 1 year old) everyone could take her on hand and she was okay with anybody. Now she can fly through whole house just to attack and bite disliked person, even when they're literally not doing anything in her vision, she just hears them in other room and immediately flies to bite someone in the ear or neck. And she bites very hard, it's not just warning but seroius bite. But despite that, she never bites my mom, she is like part of the flock. But yesterday, when my mom answered ringing phone, she just attacked her and bit her on finger really hard. Then she attacked her when she wore striped t-shirt. And today she attacked her when she just brought plate (which she's not scared at all, because parrots eat from same plates) and when she brought her computer. Well, that's a long story, but I really don't know what to do anymore.
I live in Poland, so there aren't even some professional behaviourists to help me. I can't even imagine giving them away to someone, but I can't imagine living with them closed in room all day neither. I'd really appreciate any response or help.

hey and welcome to the forum. Your English is very good. I would have never guessed it wasn't your first language. It's good to meet people who go to the trouble to fix issues with their bird instead of giving them away. Thanks for coming here and i hope we can help. I'd offer some advice but wait and see what others have to say be for you act. Maybe someone will have better suggestion .

I really think you need to clip her. You need to stop the flying and attacking . Then we can work on her aggression issues. I would assume that she lives with the three of you, your mom is the "big bird" and she bonded to you. Your sister is a threat to her relationship with you,and she senses the hostility between you. It would be good if you and your sister could work things out and get your sister to help with taming the bird down. Your mom needs to not be afraid and pick the bird up off the floor (clipped she'll like the floor even less and really need a friend to save her). The way it is now the bird is ruling the house (flock) and that needs to change. Clipping will make her depend on people more and gives you a chance to change the leadership. As long as the bird is in charge ,Chaos will be the rule. There's many things like 'clicker training" that will help her learn to be with people,trust people. Trust is the issue, she doesn't trust people to "rule" her life and make decisions. You need to show her that you can do that. Be the leader and treat her good. Give her tons of praise when she does good and the "cold shoulder" when she misbehaves. I'm sure other will have some imput, but wanted to respond to your plea for help. You've come to the right place. We'll be here for you.

After rereading your post, do you think she could be a he ,and the two conures are a pair? Many birds will pair with another bird and forsake humans. Generally the males will defend the pair. Could this be your problem?

Thank you very much for your reply. I don't think she is a he, both of my parrots were DNA tested, older was girl, so we bought her a boy. I don't know if they're a pair, but they definitely accept and like each other. They groom each other, sleep together, but both still look for contact with me, too. I'm not a fan of clipping wings, because I saw her how she was unhappy that she couldn't fly, she tried everyday until finally she could one more time learn how to fly.
Also, I forgot to add that few times we tried to show her that my sister is not an enemy, we sat and I took her out and my sister was giving her some snacks, but when my parrot got borded with food or my sister made one false move, she attacked her again.

It might work better if your sister "worked" with her when you or the other bird was not around. Maybe she won't feel the need to defend her favorite person or mate.

My sister is now on vacation trip, but when she's back we will try once again to stop my parrot's aggression. I just don' t know if it's even possible, how can I show her that all these things and people she's afraid of aren't going to hurt her. She just doesn't get it and keeps attacking, no matter if they are giving her treats and keeping distance from her.

ayakinom I understand your feeling about not clipping your birds wings But! and it's a big but your bird is abusing the privledge and attacking people and that should not be allowed it's not safe for your bird and it will lead to isolation and distrust from the rest of her flock (your family). the advice henpecked has given you is right on and you don't have to clip so much that she has no flight but just enough so that flying is a real effort for her, you can also read my post about stick training which is under the training forum. It is time for you as this birds owner to take responsibility for your birds misbehavior not to make excuses for her, mom and sister should not be under attack in their own home. Be sure to post back when you've made progress or if you need more advice.

I would agree with clipping, even if it is on a temporary basis. Georgie went through a much less dramatic period of aggression too. At that same age. She bit a lot of people (not me too much) and a lot of my family actually gave up on her at that point and never tried to befriend her again. I did have to clip her. I was told to clip them and take them away from the comfort zone where they feel most dominant (their cage and the room the cage is in) and try to gradually work with them.