There's a lot of talk lately about bailout packages being offered to airlines and other affected industries. Assuming that the president was in support of a bailout and was willing to do whatever was (legally) necessary to achieve it, and further assuming congress was strongly against it. Could the president force said bailout to happen?
Only Congress can increase or decrease the government's budget. This is enshrined in the US constitution Article I, section 9, clause 7:
No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law;
Laws are made by Congress. So if the President wants the United States to take on additional debt or increase taxes in order to fund this bailout, then Congress needs to make a law which says so.
However, since February 15th 2019 there is precedent for using an emergency declaration to reallocate funds Congress already cleared for one government program to another. On that date, the President of the United States used the declaration of a national emergency to move funds earmarked for the Department of Defense to fund border security measures at the US-Mexican border.
However, this measure was moving funds which were already allotted for one government purpose to another. It did not allow the US government to spend more money than it was allowed to according to the budget. So if the US president would use an emergency declaration in order to bail out industries affected by a disaster, and Congress wouldn't cooperate, then the President would have to decide where to take that money from.
There are existing statutes that give various bodies in the Executive Branch the authority to loan money without a Congressional appropriation or further act of law. For example, the Federal Reserve, which is not in a direct chain of command from the President, has such authority.
These loans are limited in purpose and amount, but it isn't impossible that bailouts in the form of loans could be accomplished by Executive Order, although actual spending as opposed to loans would have to be supported by some existing appropriation to be made without a new Congressional authorization.