Praise be to Allah for your coming to Islam. Allah has blessed you by making you Muslim. And praise be to Allah for the fact that you feel Allah is with you, for this is what brings peace to the heart and makes deeds righteous.
Please understand that Allah sends trials upon people so as to distinguish between them, so that it will be known who will bear them with patience and the hope of reward from Allah, and who will be filled with despair and will resent the decree of Allah. So those who are patient will be rewarded with Paradise and those who despair will be punished with torment, grief and pain in this world, before the Hereafter.
The plane crash which you mentioned is of this nature. The people on board were either committed Muslims, so this disaster is an expiation for their sins and will raise their status, as it is a kind of martyrdom (shahadah) for which they will be rewarded, and their families will be rewarded if they bear their loss with patience; or they were kuffar (disbelievers) and evildoers who did not obey their Lord, so the accident was a punishment from Allah and vengeance from Him.
A Muslim must not feel sad for the death of non-Muslims because every human being is destined to die. But dying before we Muslims were able to guide them to Islam is our source of grief and sadness because whoever is not Muslim is doomed in Hell.
There is nothing mysterious about this as you claim. It is the decree of Allah which happens at every instant; we must bear it with patience and not let grief overwhelm us. The crash of this airplane is a sign from Allah to mankind, to remind them of the greatness of the power of Allah.
Allah says concerning ships (interpretation of the meaning):
“And among His Signs are the ships in the sea like mountains.
If He wills, He causes the wind to cease, then they would become motionless on the back (of the sea). Verily, in this are signs for everyone patient and grateful.
Or He may destroy them (by shipwreck) because of that which their (people) have earned. And He pardons much.
And those who dispute (polytheists, with Our Messenger Muhammad) as regards Our Ayat (proofs, signs, verses of Islamic Monotheism) may know that there is no place of refuge for them (from Allah’s punishment)
So whatever you have been given is but (a passing) enjoyment for this worldly life, but that which is with Allah (Paradise) is better and more lasting for those who believe (in the Oneness of Allah, Islamic Monotheism) and put their trust in their Lord (concerning all of their affairs).”
Plane crashes and other disasters serve to remind people that no matter how much progress they make in earthly terms and how much strength they gain, Allah is stronger and more powerful than they are. What they do and the developments they have made will not save them from the punishment and decree of Allah if it comes to them. Let people go back and look at themselves, and realize how incapable and weak they really are, and how strong, mighty and powerful Allah is.
Please realize that Allah is close and that He responds to the call of the one who is in need. Allah does not distance Himself from man unless man distances himself from Allah and becomes arrogant.
Allah says (interpretation of the meaning):
“And when My slaves ask you (O Muhammad) concerning Me, then (answer them), I am indeed near (to them by My Knowledge). I respond to the invocations of the supplicant when he calls on Me (without any mediator or intercessor). So let them obey Me and believe in Me, so that they may be led aright.”
So no one should feel that Allah is far away from him, unless he has done something to affect the relationship between him and Allah. If he puts matters right between him and Allah, then he will not feel that grief and distance.
The feelings of grief and loneliness that have overwhelmed you are from the accursed Shaytan who wants to cause grief to those who believe; he does not want to see them active in doing actions of obedience to Allah that will bring joy to their hearts.
Al-Imam Ibn Katheer (may Allah have mercy on him) said:
Allah says (interpretation of the meaning):
“And if an evil whisper from Shaytan (Satan) tries to turn you away (O Muhammad) (from doing good), then seek refuge in Allah. Verily, He is the All‑Hearer, the All‑Knower.”
“Show forgiveness, enjoin what is good, and turn away from the foolish (i.e. don’t punish them). And if an evil whisper comes to you from Shaytan (Satan), then seek refuge with Allah. Verily, He is All-Hearer, All-Knower.”
“Repel evil with that which is better. We are Best‑Acquainted with the things they utter.
And say: ‘My Lord! I seek refuge with You from the whisperings (suggestions) of the Shayateen (devils).
And I seek refuge with You, My Lord! Lest they should come near me.’”
“Repel (the evil) with one which is better (i.e. Allah orders the faithful believers to be patient at the time of anger, and to excuse those who treat them badly) then verily he, between whom and you there was enmity, (will become) as though he was a close friend.
But none is granted it (the above quality) except those who are patient — and none is granted it except the owner of the great portion (of happiness in the Hereafter, i.e., Paradise and of a high moral character) in this world.
And if an evil whisper from Shaytan (Satan) tries to turn you away (O Muhammad) (from doing good), then seek refuge in Allah. Verily, He is the All‑Hearer, the All‑Knower.”
There is no fourth ayah (verse) with a meaning like that of these three, which is that Allah commands us to be kind to human enemies and treat them kindly so that their inherent good nature will prevail and they will become our friends. But He commands us to seek refuge with Him from satanic enemies; there is no point in being kind to them or treating them nicely, for they want only to destroy the sons of Adam because of the intensity of the enmity between them and their father Adam beforehand. Allah says (interpretation of the meaning):
“O Children of Adam! Let not Shaytan (Satan) deceive you, as he got your parents [Adam and Hawwa (Eve)] out of Paradise.”
“Surely, Shaytan (Satan) is an enemy to you, so take (treat) him as an enemy. He only invites his Hizb (followers) that they may become the dwellers of the blazing Fire.”
“Will you then take him (Iblees) and his offspring as protectors and helpers rather than Me while they are enemies to you? What an evil is the exchange for the Zalimoon (polytheists, and wrongdoers, etc).”
Iblees swore to our father Adam that he was one of the sincere, but he lied, so how about his dealings with us? Especially since he said:
“By Your Might, then I will surely mislead them all, except Your chosen slaves amongst them (i.e. faithful, obedient, true believers of Islamic Monotheism).”
[Sad 38:82-83 – interpretation of the meaning]
And Allah says (interpretation of the meaning):
“So when you want to recite the Quran, seek refuge with Allah from Shaytan (Satan), the outcast (the cursed one). Verily, he has no power over those who believe and put their trust only in their Lord (Allah). His power is only over those who obey and follow him (Satan), and those who join partners with Him (Allah, i.e. those who are Mushrikoon, i.e., polytheists.”
(Tafseer Ibn Katheer, 1/14)
So turn to Allah, remember Him and strive to worship Him, so that your soul will become pure and love for Him will become firmly entrenched in your heart, and you will be relieved of your worry and grief. Remember the hadeeth of the Prophet (peace and blessings of Allah be upon him):
The Messenger of Allah (peace and blessings of Allah be upon him) said: “There is no-one who is afflicted by distress and grief, and says: ‘Allaahumma inni ‘abduka ibn ‘abdika ibn amatika nasiyati bi yadika, madin fiyya hukmuka, ‘adlun fiyya qadauka. As’aluka bi kulli ismin huwa laka sammayta bihi nafsaka aw anzaltahu fi kitabika aw ‘allamtahu ahadan min khalqika aw istatharta bihi fi ‘ilm il-ghayb ‘indaka an taj’al al-Qurana rabee’a qalbi wa noor sadri wa jala huzni wa dhihab hammi (O Allah, I am Your slave, son of Your slave, son of Your maidservant; my forelock is in Your hand, Your command over me is forever executed and Your decree over me is just. I ask You by every name belonging to You which You have named Yourself with, or revealed in Your Book, or You taught to any of Your creation, or You have preserved in the knowledge of the Unseen with You, that You make the Quran the life of my heart and the light of my breast, and a departure for my sorrow and a release for my anxiety),’ but Allah will take away his distress and grief, and replace it with joy.” (Narrated by al-Imam Ahmad, 3704; it is a saheeh hadeeth/authentic narration). May Allah bless our Prophet Muhammad.
And Allah knows best.