I keep thinking if the Norwegians had issued a partial mobilization and a war warning, neither German nor Allied landings would be as easy as OTL. Something as easy as unpacking, assembling and staffing the crated Hawk 75's and stationing a battalion of solders at Sola/Stavanger airfield would have unhinged the German attack.
It's well before the POD, but here goes.
In the RAF threads I start, but never finish the plan was for the following:
- The first contract for 310 Spitfires from Supermarine to be completed by 31st March 1939 instead of September 1939 so that more had been delivered by the outbreak of WWII.
- The first contract for 600 Hurricanes from Hawker to be completed by 31st March 1939 instead of October 1939 so that more had been delivered from this source by the outbreak of WWII.
- The Hawker Henley was actually built by Gloster. IOTL they built 200 which were delivered between November 1938 and September 1940. 122 were on charge with the RAF in September 1939. However, most of the reference books say that 350 were ordered and I have an Air Ministry document saying that 400 were on requisition on 12th October 1936. In my timelines the Air Ministry orders 400 Hurricanes from Gloster. 244 aircraft from this order would be on charge with the RAF in September 1939.
- The same Air Ministry document says that 389 Hawker Hotspur turret fighters were on requisition from Avro on 12th October 1936. These were to be delivered by 31st March 1939 and equip 7 squadrons in Fighter Command. This was cancelled an replaced by orders for the Boulton Paul Defiant which hadn't entered service by September 1939. In my timeline 389 Hurricanes were on order from Avro in October 1936. The order was transferred to Boulton Paul later and because the Hurricane was about a year ahead of the Defiant in development Boulton Paul had been able to deliver all 389 by September 1939.
- 746 Gloster Gladiators were built for the RAF, FAA and export IOTL.
- The first RAF Gladiator squadron was formed in February 1937 only 10 months before the first Hurricane squadron and only 3 months before the first Battle squadron. I mention the Fairey Battle because it was the first Merlin powered aircraft to go into service.
- The first 225 Gladiators ordered for the RAF were ordered in July 1935 (23 to Contract 419392/35) and September 1935 (202 to Contract 442476/35) but 22 aircraft in the second contract were either cancelled or more likely were the 22 supplied to Belgium, which reduced the total to 203. These were delivered to the RAF between February 1937 and January 1938 (or February 1938 depending on the source).
- The next order for 78 Gladiators (to Contract 704393/37) wasn't placed until sometime in 1936. (I don't know the exact date but going by the contract number it is likely to have been between 1st April 1936 and 31st March 1937). The first 28 were delivered in September 1938, which is only 2 months before the first Gloster built Henley. The last 50 were delivered between December 1938 and February 1939. Of the 78 aircraft built 40 went to the RAF proper and 38 were completed as Sea Gladiators for the FAA.
- The final order for 300 Gladiators (to Contract 952950/38) was probably placed sometime in 1938. (I don't know the exact date but going by the contract number it is likely to have been between 1st April 1938 and 31st March 1939.) 21 were used to fill export contracts (6 to Norway and 15 to Portugal), which left 279 to be delivered to the RAF (219) and FAA (60). Deliveries were between March 1939 and April 1940.
- Of the 603 Gladiators ordered to Air Ministry contracts only 560 were actually delivered to the RAF and FAA because 43 were used to fill export contracts (22 Belgium, 6 Norway and 15 Portugal). A grand total 186 of "first hand" Gladiators were exported, which brought the total number of Gladiators built to 746 plus the prototype. The export contracts include 12 aircraft built for Norway, which included 6 diverted from RAF contracts.
- A Cabinet Paper that I downloaded from the National Archives, which is dated 17th May 1935. It says that the first flights of the prototype Hurricane and Spitfire were expected in July and October 1935 respectively. IOTL they were actually November 1935 and March 1936. In my timelines the Hurricane and Spitfire prototypes meet their projected first flight dates.
- In my timeline Gloster builds another 746 Hurricanes for the RAF, FAA and export instead of the 746 Gladiators of OTL. The first contract for 23 aircraft and possibly the second contract for 202 aircraft are still placed. However, the earlier first flight of the Hurricane leads the Air Ministry to cancel all its Gladiator orders and replaces them with orders for Hurricanes to be built by Gloster.
- OTL Gloster built 2,750 Hurricanes. ITTL the 1,146 aircraft built instead of the Gladiator and Henley increase the total to 3,896 aircraft.
- ITTL the Westland Lysander is still built to Specification A.39/34. However, the RAF's army co-operation doctrine changes between 1934 and the placing of the first production contract in 1936. Instead of replacing the modified light bombers used for army co-operation with the Lysander it decides to replace them with Westland built Hurricanes modified for ground attack and use a modified commercial light aircraft for the AOP role.
The upshot of all that is that Norway buys 12 Hurricanes instead of the 12 Gladiators that it bought IOTL and all other things being equal 7 were ready to defend Oslo when the Luftwaffe appeared overhead.
I haven't checked by sources, so the next part will have to be an IIRC. Norway placed an initial order for 36 Curtis Hawks, which depending on the source was brought up to 60 or 84 by subsequent orders.
From 1937 ITTL Hawker Siddeley, Boulton Paul and Westland are building Hurricanes like there's no tomorrow. The RAF Fighter Command and the fighter squadrons overseas receive the quotas of Hurricanes they require under Expansion Scheme F by March 1939 so that there are plenty of aircraft available for export. As a result the Norwegians buy 84 Hurricanes diverted from Air Ministry contracts instead of the 60-84 Hawks of OTL. They do so because of commonality with the 12 Hurricanes that they already have so it makes maintenance and training easier, but mainly because the British can delivery them much earlier than Curtiss can deliver its Hawks.
All 84 aircraft would have been delivered by early April 1940, but not all of them would have been in front-line units. Their presence would not have deterred the Germans from invading ITTL because they were still relying on surprise. However, it is the Germans that would be surprised because instead of 7 Gladiators taking off to defend Oslo it would be a multiple of Hurricanes. I usually say 28 Hurricanes from the first 48 delivered (i.e. 12 instead of the Gladiators and 36 instead of the first 36 Hawks) met the Germans.
OTL the Swedes bought 55 Gladiators which were delivered 1937-38 and in my TL they buy 55 Hurricanes.
OTL the British supplied the Finns with 12 Hurricanes, 30 Gladiators, 25 Gloster Gauntlet biplane fighters and 3 Westland Lysanders (a total of 70 aircraft) from RAF stocks to help them fight the Russians. The Gladiators and Gauntlet's were ex-RAF aircraft. In my TL 70 Hurricanes are sent.