4 month old puppy terribly afraid of outside

We’ve had our Mastiff girl since she was ten weeks old and she turns 16 weeks old tomorrow. She has honestly been a dream but is our first puppy in over 10 years. Initially when she arrived she was a bit scared of a few things that she hadn’t been exposed to as we live in acreage and she was born in suburbia. They were mainly things that made loud noises like tractors. A few weeks ago we were in the back paddock and a helicopter came over. It spooked her but she was happy to stay outside. I didn’t think anything of it as she has had similar reactions to neighbours horses trotting in the paddock and so on – sort of like getting a fright when she sees something for the first time but quickly getting over it and no lasting effects. Happy to take reassurance from myself. She no longer really cares about tractors or loud cars, so on.

But yesterday morning two low flying fire fighting choppers came over back to back and my girl has been terrified since. She wasn’t even outside properly for the choppers but was on the deck. She was pretty much toilet trained but now doesn’t even want to go out side and has had more accidents inside in the last 24 hours than she has in weeks. Ones I believe with that are out of pure fear ie last night she peed in them middle of the kitchen, she has never done that. The wee I can deal with but the pure fear in her eyes is absolutely breaking my heart. It’s made her so on edge and very nervous of noises. We live in the Hills and have flocks of black cockatoos that visit seasonally which are extremely noisy so I’m wondering if they are adding to her aversion as they are in the trees squawking all day. Tonight she watched our other dog play on the front lawn but wouldn’t come down off the deck. She did spend some time on the deck today and in the small fenced off backyard we have but only when absolutely necessary.

Yesterday afternoon when I took her for a walk in back paddock, a motorbike came past somewhere in the neighbourhood which spooked her and then a plane came overhead which has happened countless of times, but it was enough for her to tuck up and run home. I’m now worried about how to tackle this going forward as it seems everytime we go outside we just end up having another negative experience.

How do I overcome this? Just lots of treats, time? Feed her outside so she builds a more positive association? We take her places atleast 3 times a week but I haven’t for a few days but need to tomorrow, should I or will it be best to leave her at home?